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	$47.64	10.511%	$52.6474	$52.65	$52.65	$52.60
Purchase #2	$199.44	6.408%	$212.2201	$212.22	$212.20	$212.20
Purchase #3	$111.75	12.388%	$125.5936	$125.59	$125.60	$125.60
Purchase #4	$113.78	12.349%	$127.8307	$127.83	$127.85	$127.80
Purchase #5	$98.83	6.796%	$105.5465	$105.55	$105.55	$105.50
Purchase #6	$213.79	10.345%	$235.9066	$235.91	$235.90	$235.90
Purchase #7	$248.73	13.172%	$281.4927	$281.49	$281.50	$281.50
7 purchase totals =	$1,033.96		$1,141.2376	$1,141.24	$1,141.25	$1,141.10