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	$131.94	11.668%	$147.3348	$147.33	$147.35	$147.30
Purchase #2	$68.35	13.149%	$77.3373	$77.34	$77.35	$77.30
Purchase #3	$194.37	13.482%	$220.575	$220.58	$220.60	$220.60
Purchase #4	$180.45	10.736%	$199.8231	$199.82	$199.80	$199.80
Purchase #5	$82.53	9.443%	$90.3233	$90.32	$90.30	$90.30
Purchase #6	$243.98	3.760%	$253.1536	$253.15	$253.15	$253.20
Purchase #7	$44.30	10.212%	$48.8239	$48.82	$48.80	$48.80
7 purchase totals =	$945.92		$1,037.3710	$1,037.36	$1,037.35	$1,037.30