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	$148.36	5.749%	$156.8892	$156.89	$156.90	$156.90
Purchase #2	$96.25	10.383%	$106.2436	$106.24	$106.25	$106.20
Purchase #3	$151.31	11.375%	$168.5215	$168.52	$168.50	$168.50
Purchase #4	$41.27	8.763%	$44.8865	$44.89	$44.90	$44.90
Purchase #5	$135.46	8.317%	$146.7262	$146.73	$146.75	$146.70
Purchase #6	$132.88	6.221%	$141.1465	$141.15	$141.15	$141.10
Purchase #7	$129.85	8.404%	$140.7626	$140.76	$140.75	$140.80
7 purchase totals =	$835.38		$905.1761	$905.18	$905.20	$905.10