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	$166.47	13.255%	$188.5356	$188.54	$188.55	$188.50
Purchase #2	$222.99	13.569%	$253.2475	$253.25	$253.25	$253.20
Purchase #3	$92.61	11.626%	$103.3768	$103.38	$103.40	$103.40
Purchase #4	$12.33	7.349%	$13.2361	$13.24	$13.25	$13.20
Purchase #5	$211.54	12.534%	$238.0544	$238.05	$238.05	$238.10
Purchase #6	$165.32	5.319%	$174.1134	$174.11	$174.10	$174.10
Purchase #7	$150.39	13.856%	$171.228	$171.23	$171.25	$171.20
7 purchase totals =	$1,021.65		$1,141.7918	$1,141.80	$1,141.85	$1,141.70