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	$248.90	3.215%	$256.9021	$256.90	$256.90	$256.90
Purchase #2	$202.82	4.754%	$212.4621	$212.46	$212.45	$212.50
Purchase #3	$148.35	11.544%	$165.4755	$165.48	$165.50	$165.50
Purchase #4	$36.49	3.206%	$37.6599	$37.66	$37.65	$37.70
Purchase #5	$245.36	7.769%	$264.422	$264.42	$264.40	$264.40
Purchase #6	$219.88	10.665%	$243.3302	$243.33	$243.35	$243.30
Purchase #7	$95.29	3.751%	$98.8643	$98.86	$98.85	$98.90
7 purchase totals =	$1,197.09		$1,279.1161	$1,279.11	$1,279.10	$1,279.20