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	$117.39	9.646%	$128.7134	$128.71	$128.70	$128.70
Purchase #2	$249.46	9.607%	$273.4256	$273.43	$273.45	$273.40
Purchase #3	$229.34	12.718%	$258.5075	$258.51	$258.50	$258.50
Purchase #4	$55.87	7.283%	$59.939	$59.94	$59.95	$59.90
Purchase #5	$81.29	9.369%	$88.9061	$88.91	$88.90	$88.90
Purchase #6	$115.42	12.199%	$129.5001	$129.50	$129.50	$129.50
Purchase #7	$194.99	5.535%	$205.7827	$205.78	$205.80	$205.80
7 purchase totals =	$1,043.76		$1,144.7744	$1,144.78	$1,144.80	$1,144.70