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	$230.29	10.333%	$254.0859	$254.09	$254.10	$254.10
Purchase #2	$17.54	13.137%	$19.8442	$19.84	$19.85	$19.80
Purchase #3	$134.77	8.562%	$146.309	$146.31	$146.30	$146.30
Purchase #4	$184.30	6.840%	$196.9061	$196.91	$196.90	$196.90
Purchase #5	$46.98	13.480%	$53.3129	$53.31	$53.30	$53.30
Purchase #6	$171.56	11.493%	$191.2774	$191.28	$191.30	$191.30
Purchase #7	$131.77	8.800%	$143.3658	$143.37	$143.35	$143.40
7 purchase totals =	$917.21		$1,005.1013	$1,005.11	$1,005.10	$1,005.10