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	$221.84	5.196%	$233.3668	$233.37	$233.35	$233.40
Purchase #2	$91.62	6.287%	$97.3801	$97.38	$97.40	$97.40
Purchase #3	$159.87	13.159%	$180.9073	$180.91	$180.90	$180.90
Purchase #4	$64.49	10.131%	$71.0235	$71.02	$71.00	$71.00
Purchase #5	$192.88	9.430%	$211.0686	$211.07	$211.05	$211.10
Purchase #6	$151.71	12.263%	$170.3142	$170.31	$170.30	$170.30
Purchase #7	$78.92	6.223%	$83.8312	$83.83	$83.85	$83.80
7 purchase totals =	$961.33		$1,047.8917	$1,047.89	$1,047.85	$1,047.90