Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$188.46	11.752%	$210.6078	$210.61	$210.60	$210.60
Purchase #2	$91.88	10.372%	$101.4098	$101.41	$101.40	$101.40
Purchase #3	$141.44	6.734%	$150.9646	$150.96	$150.95	$151.00
Purchase #4	$115.29	9.354%	$126.0742	$126.07	$126.05	$126.10
Purchase #5	$243.62	8.736%	$264.9026	$264.90	$264.90	$264.90
Purchase #6	$126.45	11.826%	$141.404	$141.40	$141.40	$141.40
Purchase #7	$148.38	12.362%	$166.7227	$166.72	$166.70	$166.70
7 purchase totals =	$1,055.52		$1,162.0857	$1,162.07	$1,162.00	$1,162.10