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	$117.72	13.856%	$134.0313	$134.03	$134.05	$134.00
Purchase #2	$203.83	9.209%	$222.6007	$222.60	$222.60	$222.60
Purchase #3	$232.29	4.308%	$242.2971	$242.30	$242.30	$242.30
Purchase #4	$213.59	9.343%	$233.5457	$233.55	$233.55	$233.50
Purchase #5	$40.35	12.339%	$45.3288	$45.33	$45.35	$45.30
Purchase #6	$127.82	9.448%	$139.8964	$139.90	$139.90	$139.90
Purchase #7	$47.35	6.450%	$50.4041	$50.40	$50.40	$50.40
7 purchase totals =	$982.95		$1,068.1041	$1,068.11	$1,068.15	$1,068.00