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	$113.87	11.257%	$126.6883	$126.69	$126.70	$126.70
Purchase #2	$60.52	11.235%	$67.3194	$67.32	$67.30	$67.30
Purchase #3	$232.61	10.125%	$256.1618	$256.16	$256.15	$256.20
Purchase #4	$166.33	11.751%	$185.8754	$185.88	$185.90	$185.90
Purchase #5	$121.27	5.278%	$127.6706	$127.67	$127.65	$127.70
Purchase #6	$240.27	4.142%	$250.222	$250.22	$250.20	$250.20
Purchase #7	$43.33	12.844%	$48.8953	$48.90	$48.90	$48.90
7 purchase totals =	$978.20		$1,062.8328	$1,062.84	$1,062.80	$1,062.90