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	$148.38	11.192%	$164.9867	$164.99	$165.00	$165.00
Purchase #2	$69.72	3.306%	$72.0249	$72.02	$72.00	$72.00
Purchase #3	$181.26	8.221%	$196.1614	$196.16	$196.15	$196.20
Purchase #4	$171.88	13.304%	$194.7469	$194.75	$194.75	$194.70
Purchase #5	$55.37	4.515%	$57.87	$57.87	$57.85	$57.90
Purchase #6	$150.99	9.596%	$165.479	$165.48	$165.50	$165.50
Purchase #7	$67.65	12.453%	$76.0745	$76.07	$76.05	$76.10
7 purchase totals =	$845.25		$927.3434	$927.34	$927.30	$927.40