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	$173.40	8.182%	$187.5876	$187.59	$187.60	$187.60
Purchase #2	$96.78	7.575%	$104.1111	$104.11	$104.10	$104.10
Purchase #3	$84.54	6.645%	$90.1577	$90.16	$90.15	$90.20
Purchase #4	$22.50	10.586%	$24.8819	$24.88	$24.90	$24.90
Purchase #5	$193.41	11.506%	$215.6638	$215.66	$215.65	$215.70
Purchase #6	$139.82	11.287%	$155.6015	$155.60	$155.60	$155.60
Purchase #7	$227.98	7.538%	$245.1651	$245.17	$245.15	$245.20
7 purchase totals =	$938.43		$1,023.1687	$1,023.17	$1,023.15	$1,023.30