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	$103.47	4.107%	$107.7195	$107.72	$107.70	$107.70
Purchase #2	$231.52	13.406%	$262.5576	$262.56	$262.55	$262.60
Purchase #3	$227.43	5.134%	$239.1063	$239.11	$239.10	$239.10
Purchase #4	$200.54	5.275%	$211.1185	$211.12	$211.10	$211.10
Purchase #5	$9.32	9.501%	$10.2055	$10.21	$10.20	$10.20
Purchase #6	$55.90	6.696%	$59.6431	$59.64	$59.65	$59.60
Purchase #7	$120.28	9.645%	$131.881	$131.88	$131.90	$131.90
7 purchase totals =	$948.46		$1,022.2315	$1,022.24	$1,022.20	$1,022.20