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	$185.45	5.234%	$195.1565	$195.16	$195.15	$195.20
Purchase #2	$91.83	8.209%	$99.3683	$99.37	$99.35	$99.40
Purchase #3	$229.93	7.179%	$246.4367	$246.44	$246.45	$246.40
Purchase #4	$177.98	7.801%	$191.8642	$191.86	$191.85	$191.90
Purchase #5	$49.91	5.429%	$52.6196	$52.62	$52.60	$52.60
Purchase #6	$124.86	7.736%	$134.5192	$134.52	$134.50	$134.50
Purchase #7	$153.68	11.373%	$171.158	$171.16	$171.15	$171.20
7 purchase totals =	$1,013.64		$1,091.1225	$1,091.13	$1,091.05	$1,091.20