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	$98.84	12.108%	$110.8075	$110.81	$110.80	$110.80
Purchase #2	$221.37	9.566%	$242.5463	$242.55	$242.55	$242.50
Purchase #3	$119.64	6.793%	$127.7671	$127.77	$127.75	$127.80
Purchase #4	$9.54	11.393%	$10.6269	$10.63	$10.65	$10.60
Purchase #5	$180.70	6.429%	$192.3172	$192.32	$192.30	$192.30
Purchase #6	$195.67	4.444%	$204.3656	$204.37	$204.35	$204.40
Purchase #7	$152.67	12.735%	$172.1125	$172.11	$172.10	$172.10
7 purchase totals =	$978.43		$1,060.5431	$1,060.56	$1,060.50	$1,060.50