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	$61.53	9.716%	$67.5083	$67.51	$67.50	$67.50
Purchase #2	$194.59	8.709%	$211.5368	$211.54	$211.55	$211.50
Purchase #3	$169.56	11.327%	$188.7661	$188.77	$188.75	$188.80
Purchase #4	$7.36	3.106%	$7.5886	$7.59	$7.60	$7.60
Purchase #5	$133.91	12.464%	$150.6005	$150.60	$150.60	$150.60
Purchase #6	$168.46	10.151%	$185.5604	$185.56	$185.55	$185.60
Purchase #7	$23.87	10.157%	$26.2945	$26.29	$26.30	$26.30
7 purchase totals =	$759.28		$837.8552	$837.86	$837.85	$837.90