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	$125.54	4.701%	$131.4416	$131.44	$131.45	$131.40
Purchase #2	$34.98	10.505%	$38.6546	$38.65	$38.65	$38.70
Purchase #3	$57.87	11.386%	$64.4591	$64.46	$64.45	$64.50
Purchase #4	$54.63	4.181%	$56.9141	$56.91	$56.90	$56.90
Purchase #5	$154.49	7.274%	$165.7276	$165.73	$165.75	$165.70
Purchase #6	$187.55	4.592%	$196.1623	$196.16	$196.15	$196.20
Purchase #7	$86.35	6.169%	$91.6769	$91.68	$91.70	$91.70
7 purchase totals =	$701.41		$745.0362	$745.03	$745.05	$745.10