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	$120.90	4.283%	$126.0781	$126.08	$126.10	$126.10
Purchase #2	$43.31	8.370%	$46.935	$46.94	$46.95	$46.90
Purchase #3	$231.89	11.317%	$258.133	$258.13	$258.15	$258.10
Purchase #4	$172.63	11.562%	$192.5895	$192.59	$192.60	$192.60
Purchase #5	$89.76	11.865%	$100.41	$100.41	$100.40	$100.40
Purchase #6	$235.33	4.164%	$245.1291	$245.13	$245.15	$245.10
Purchase #7	$247.82	7.538%	$266.5007	$266.50	$266.50	$266.50
7 purchase totals =	$1,141.64		$1,235.7754	$1,235.78	$1,235.85	$1,235.70