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	$152.85	10.501%	$168.9008	$168.90	$168.90	$168.90
Purchase #2	$237.72	6.870%	$254.0514	$254.05	$254.05	$254.10
Purchase #3	$104.94	7.166%	$112.46	$112.46	$112.45	$112.50
Purchase #4	$61.65	11.684%	$68.8532	$68.85	$68.85	$68.90
Purchase #5	$17.60	5.870%	$18.6331	$18.63	$18.65	$18.60
Purchase #6	$148.76	7.658%	$160.152	$160.15	$160.15	$160.20
Purchase #7	$7.54	7.315%	$8.0916	$8.09	$8.10	$8.10
7 purchase totals =	$731.06		$791.1421	$791.13	$791.15	$791.30