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	$174.51	12.688%	$196.6518	$196.65	$196.65	$196.70
Purchase #2	$100.89	8.362%	$109.3264	$109.33	$109.35	$109.30
Purchase #3	$168.90	11.119%	$187.68	$187.68	$187.70	$187.70
Purchase #4	$29.50	13.358%	$33.4406	$33.44	$33.45	$33.40
Purchase #5	$47.67	12.374%	$53.5687	$53.57	$53.55	$53.60
Purchase #6	$108.87	4.392%	$113.6516	$113.65	$113.65	$113.70
Purchase #7	$215.54	13.332%	$244.2758	$244.28	$244.30	$244.30
7 purchase totals =	$845.88		$938.5949	$938.60	$938.65	$938.70