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	$182.73	11.621%	$203.9651	$203.97	$203.95	$204.00
Purchase #2	$57.38	3.295%	$59.2707	$59.27	$59.25	$59.30
Purchase #3	$218.59	12.358%	$245.6034	$245.60	$245.60	$245.60
Purchase #4	$225.85	3.713%	$234.2358	$234.24	$234.25	$234.20
Purchase #5	$96.90	5.782%	$102.5028	$102.50	$102.50	$102.50
Purchase #6	$25.60	6.111%	$27.1644	$27.16	$27.15	$27.20
Purchase #7	$141.47	7.777%	$152.4721	$152.47	$152.45	$152.50
7 purchase totals =	$948.52		$1,025.2143	$1,025.21	$1,025.15	$1,025.30