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	$218.81	12.260%	$245.6361	$245.64	$245.65	$245.60
Purchase #2	$118.60	9.732%	$130.1422	$130.14	$130.15	$130.10
Purchase #3	$209.54	13.758%	$238.3685	$238.37	$238.35	$238.40
Purchase #4	$145.69	3.861%	$151.3151	$151.32	$151.30	$151.30
Purchase #5	$50.34	4.518%	$52.6144	$52.61	$52.60	$52.60
Purchase #6	$123.52	3.585%	$127.9482	$127.95	$127.95	$127.90
Purchase #7	$130.65	6.206%	$138.7581	$138.76	$138.75	$138.80
7 purchase totals =	$997.15		$1,084.7826	$1,084.79	$1,084.75	$1,084.70