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	$141.57	4.670%	$148.1813	$148.18	$148.20	$148.20
Purchase #2	$42.91	4.546%	$44.8607	$44.86	$44.85	$44.90
Purchase #3	$115.89	9.737%	$127.1742	$127.17	$127.15	$127.20
Purchase #4	$177.74	6.211%	$188.7794	$188.78	$188.80	$188.80
Purchase #5	$173.62	8.551%	$188.4662	$188.47	$188.45	$188.50
Purchase #6	$181.55	7.718%	$195.562	$195.56	$195.55	$195.60
Purchase #7	$106.29	7.499%	$114.2607	$114.26	$114.25	$114.30
7 purchase totals =	$939.57		$1,007.2845	$1,007.28	$1,007.25	$1,007.50