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	$248.38	4.362%	$259.2143	$259.21	$259.20	$259.20
Purchase #2	$7.58	3.872%	$7.8735	$7.87	$7.85	$7.90
Purchase #3	$194.31	7.872%	$209.6061	$209.61	$209.60	$209.60
Purchase #4	$69.85	3.381%	$72.2116	$72.21	$72.20	$72.20
Purchase #5	$62.86	11.785%	$70.2681	$70.27	$70.25	$70.30
Purchase #6	$144.78	4.700%	$151.5847	$151.58	$151.60	$151.60
Purchase #7	$203.64	7.435%	$218.7806	$218.78	$218.80	$218.80
7 purchase totals =	$931.40		$989.5389	$989.53	$989.50	$989.60