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	$200.58	11.431%	$223.5083	$223.51	$223.50	$223.50
Purchase #2	$72.56	12.112%	$81.3485	$81.35	$81.35	$81.30
Purchase #3	$134.75	13.118%	$152.4265	$152.43	$152.45	$152.40
Purchase #4	$203.86	4.154%	$212.3283	$212.33	$212.35	$212.30
Purchase #5	$236.74	12.131%	$265.4589	$265.46	$265.45	$265.50
Purchase #6	$52.29	6.436%	$55.6554	$55.66	$55.65	$55.70
Purchase #7	$53.43	11.120%	$59.3714	$59.37	$59.35	$59.40
7 purchase totals =	$954.21		$1,050.0973	$1,050.11	$1,050.10	$1,050.10