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	$36.60	5.268%	$38.5281	$38.53	$38.55	$38.50
Purchase #2	$56.50	4.141%	$58.8397	$58.84	$58.85	$58.80
Purchase #3	$35.81	9.223%	$39.1128	$39.11	$39.10	$39.10
Purchase #4	$47.84	4.728%	$50.1019	$50.10	$50.10	$50.10
Purchase #5	$77.36	6.123%	$82.0968	$82.10	$82.10	$82.10
Purchase #6	$101.88	11.179%	$113.2692	$113.27	$113.25	$113.30
Purchase #7	$74.34	8.807%	$80.8871	$80.89	$80.90	$80.90
7 purchase totals =	$430.33		$462.8356	$462.84	$462.85	$462.80