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	$163.50	4.602%	$171.0243	$171.02	$171.00	$171.00
Purchase #2	$195.91	13.692%	$222.734	$222.73	$222.75	$222.70
Purchase #3	$243.55	11.689%	$272.0186	$272.02	$272.00	$272.00
Purchase #4	$79.43	12.662%	$89.4874	$89.49	$89.50	$89.50
Purchase #5	$142.46	12.136%	$159.7489	$159.75	$159.75	$159.70
Purchase #6	$167.59	11.854%	$187.4561	$187.46	$187.45	$187.50
Purchase #7	$71.42	9.693%	$78.3427	$78.34	$78.35	$78.30
7 purchase totals =	$1,063.86		$1,180.8120	$1,180.81	$1,180.80	$1,180.70