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	$177.47	4.192%	$184.9095	$184.91	$184.90	$184.90
Purchase #2	$53.88	10.222%	$59.3876	$59.39	$59.40	$59.40
Purchase #3	$82.81	7.195%	$88.7682	$88.77	$88.75	$88.80
Purchase #4	$17.78	3.271%	$18.3616	$18.36	$18.35	$18.40
Purchase #5	$113.29	9.403%	$123.9427	$123.94	$123.95	$123.90
Purchase #6	$21.34	6.814%	$22.7941	$22.79	$22.80	$22.80
Purchase #7	$175.69	12.761%	$198.1098	$198.11	$198.10	$198.10
7 purchase totals =	$642.26		$696.2735	$696.27	$696.25	$696.30