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	$41.87	8.809%	$45.5583	$45.56	$45.55	$45.60
Purchase #2	$179.34	9.449%	$196.2858	$196.29	$196.30	$196.30
Purchase #3	$24.44	13.316%	$27.6944	$27.69	$27.70	$27.70
Purchase #4	$19.29	10.234%	$21.2641	$21.26	$21.25	$21.30
Purchase #5	$191.33	4.207%	$199.3793	$199.38	$199.40	$199.40
Purchase #6	$128.36	3.517%	$132.8744	$132.87	$132.85	$132.90
Purchase #7	$243.69	10.600%	$269.5211	$269.52	$269.50	$269.50
7 purchase totals =	$828.32		$892.5774	$892.57	$892.55	$892.70