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	$226.71	7.707%	$244.1825	$244.18	$244.20	$244.20
Purchase #2	$182.79	6.282%	$194.2729	$194.27	$194.25	$194.30
Purchase #3	$50.87	4.628%	$53.2243	$53.22	$53.20	$53.20
Purchase #4	$37.93	13.102%	$42.8996	$42.90	$42.90	$42.90
Purchase #5	$76.92	11.367%	$85.6635	$85.66	$85.65	$85.70
Purchase #6	$235.67	13.764%	$268.1076	$268.11	$268.10	$268.10
Purchase #7	$134.79	11.720%	$150.5874	$150.59	$150.60	$150.60
7 purchase totals =	$945.68		$1,038.9378	$1,038.93	$1,038.90	$1,039.00