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	$243.57	10.210%	$268.4385	$268.44	$268.45	$268.40
Purchase #2	$165.26	6.173%	$175.4615	$175.46	$175.45	$175.50
Purchase #3	$49.69	12.482%	$55.8923	$55.89	$55.90	$55.90
Purchase #4	$240.78	6.541%	$256.5294	$256.53	$256.55	$256.50
Purchase #5	$79.38	5.120%	$83.4443	$83.44	$83.45	$83.40
Purchase #6	$156.30	8.600%	$169.7418	$169.74	$169.75	$169.70
Purchase #7	$149.74	3.770%	$155.3852	$155.39	$155.40	$155.40
7 purchase totals =	$1,084.72		$1,164.8930	$1,164.89	$1,164.95	$1,164.80