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	$136.58	10.486%	$150.9018	$150.90	$150.90	$150.90
Purchase #2	$90.95	13.562%	$103.2846	$103.28	$103.30	$103.30
Purchase #3	$181.77	5.700%	$192.1309	$192.13	$192.15	$192.10
Purchase #4	$133.31	10.650%	$147.5075	$147.51	$147.50	$147.50
Purchase #5	$94.66	13.539%	$107.476	$107.48	$107.50	$107.50
Purchase #6	$105.50	11.717%	$117.8614	$117.86	$117.85	$117.90
Purchase #7	$196.26	4.630%	$205.3468	$205.35	$205.35	$205.30
7 purchase totals =	$939.03		$1,024.5090	$1,024.51	$1,024.55	$1,024.50