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	$67.94	6.514%	$72.3656	$72.37	$72.35	$72.40
Purchase #2	$224.43	11.282%	$249.7502	$249.75	$249.75	$249.80
Purchase #3	$98.59	7.145%	$105.6343	$105.63	$105.65	$105.60
Purchase #4	$61.31	8.666%	$66.6231	$66.62	$66.60	$66.60
Purchase #5	$55.93	4.220%	$58.2902	$58.29	$58.30	$58.30
Purchase #6	$165.84	11.480%	$184.8784	$184.88	$184.90	$184.90
Purchase #7	$99.89	8.846%	$108.7263	$108.73	$108.75	$108.70
7 purchase totals =	$773.93		$846.2681	$846.27	$846.30	$846.30