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	$176.75	6.526%	$188.2847	$188.28	$188.30	$188.30
Purchase #2	$99.67	6.680%	$106.328	$106.33	$106.35	$106.30
Purchase #3	$40.77	3.327%	$42.1264	$42.13	$42.15	$42.10
Purchase #4	$197.76	6.518%	$210.65	$210.65	$210.65	$210.70
Purchase #5	$152.40	11.327%	$169.6623	$169.66	$169.65	$169.70
Purchase #6	$52.67	13.199%	$59.6219	$59.62	$59.60	$59.60
Purchase #7	$195.51	7.160%	$209.5085	$209.51	$209.50	$209.50
7 purchase totals =	$915.53		$986.1818	$986.18	$986.20	$986.20