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	$193.41	8.289%	$209.4418	$209.44	$209.45	$209.40
Purchase #2	$190.83	10.364%	$210.6076	$210.61	$210.60	$210.60
Purchase #3	$173.73	9.139%	$189.6072	$189.61	$189.60	$189.60
Purchase #4	$195.72	4.283%	$204.1027	$204.10	$204.10	$204.10
Purchase #5	$134.33	12.709%	$151.402	$151.40	$151.40	$151.40
Purchase #6	$77.25	8.385%	$83.7274	$83.73	$83.75	$83.70
Purchase #7	$98.77	3.796%	$102.5193	$102.52	$102.50	$102.50
7 purchase totals =	$1,064.04		$1,151.4080	$1,151.41	$1,151.40	$1,151.30