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	$147.97	9.541%	$162.0878	$162.09	$162.10	$162.10
Purchase #2	$39.41	8.854%	$42.8994	$42.90	$42.90	$42.90
Purchase #3	$213.27	9.510%	$233.552	$233.55	$233.55	$233.60
Purchase #4	$86.66	10.232%	$95.5271	$95.53	$95.55	$95.50
Purchase #5	$176.98	7.290%	$189.8818	$189.88	$189.90	$189.90
Purchase #6	$77.88	9.528%	$85.3004	$85.30	$85.30	$85.30
Purchase #7	$88.64	10.369%	$97.8311	$97.83	$97.85	$97.80
7 purchase totals =	$830.81		$907.0796	$907.08	$907.15	$907.10