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	$234.90	13.699%	$267.079	$267.08	$267.10	$267.10
Purchase #2	$175.60	10.414%	$193.887	$193.89	$193.90	$193.90
Purchase #3	$220.43	7.275%	$236.4663	$236.47	$236.45	$236.50
Purchase #4	$54.43	4.601%	$56.9343	$56.93	$56.95	$56.90
Purchase #5	$92.56	12.507%	$104.1365	$104.14	$104.15	$104.10
Purchase #6	$65.98	10.297%	$72.774	$72.77	$72.75	$72.80
Purchase #7	$85.44	3.346%	$88.2988	$88.30	$88.30	$88.30
7 purchase totals =	$929.34		$1,019.5759	$1,019.58	$1,019.60	$1,019.60