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	$203.95	3.610%	$211.3126	$211.31	$211.30	$211.30
Purchase #2	$182.96	7.470%	$196.6271	$196.63	$196.65	$196.60
Purchase #3	$33.96	6.143%	$36.0462	$36.05	$36.05	$36.00
Purchase #4	$174.88	12.197%	$196.2101	$196.21	$196.20	$196.20
Purchase #5	$28.62	7.153%	$30.6672	$30.67	$30.65	$30.70
Purchase #6	$79.45	12.710%	$89.5481	$89.55	$89.55	$89.50
Purchase #7	$45.88	3.173%	$47.3358	$47.34	$47.35	$47.30
7 purchase totals =	$749.70		$807.7471	$807.76	$807.75	$807.60