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	$94.79	7.211%	$101.6253	$101.63	$101.65	$101.60
Purchase #2	$83.72	13.210%	$94.7794	$94.78	$94.80	$94.80
Purchase #3	$149.36	11.823%	$167.0188	$167.02	$167.00	$167.00
Purchase #4	$140.59	11.278%	$156.4457	$156.45	$156.45	$156.40
Purchase #5	$104.74	4.103%	$109.0375	$109.04	$109.05	$109.00
Purchase #6	$67.87	7.217%	$72.7682	$72.77	$72.75	$72.80
Purchase #7	$63.50	6.554%	$67.6618	$67.66	$67.65	$67.70
7 purchase totals =	$704.57		$769.3367	$769.35	$769.35	$769.30