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	$113.58	12.228%	$127.4686	$127.47	$127.45	$127.50
Purchase #2	$84.29	9.104%	$91.9638	$91.96	$91.95	$92.00
Purchase #3	$85.35	4.611%	$89.2855	$89.29	$89.30	$89.30
Purchase #4	$194.32	7.758%	$209.3953	$209.40	$209.40	$209.40
Purchase #5	$244.37	6.466%	$260.171	$260.17	$260.15	$260.20
Purchase #6	$37.54	5.251%	$39.5112	$39.51	$39.50	$39.50
Purchase #7	$176.28	8.867%	$191.9107	$191.91	$191.90	$191.90
7 purchase totals =	$935.73		$1,009.7061	$1,009.71	$1,009.65	$1,009.80