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	$157.56	6.712%	$168.1354	$168.14	$168.15	$168.10
Purchase #2	$15.41	9.586%	$16.8872	$16.89	$16.90	$16.90
Purchase #3	$47.40	13.191%	$53.6525	$53.65	$53.65	$53.70
Purchase #4	$17.35	12.580%	$19.5326	$19.53	$19.55	$19.50
Purchase #5	$123.54	8.594%	$134.157	$134.16	$134.15	$134.20
Purchase #6	$85.71	4.746%	$89.7778	$89.78	$89.80	$89.80
Purchase #7	$142.76	3.192%	$147.3169	$147.32	$147.30	$147.30
7 purchase totals =	$589.73		$629.4594	$629.47	$629.50	$629.50