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	$211.80	5.504%	$223.4575	$223.46	$223.45	$223.50
Purchase #2	$226.39	7.588%	$243.5685	$243.57	$243.55	$243.60
Purchase #3	$152.36	12.505%	$171.4126	$171.41	$171.40	$171.40
Purchase #4	$83.82	6.854%	$89.565	$89.57	$89.55	$89.60
Purchase #5	$240.34	12.410%	$270.1662	$270.17	$270.15	$270.20
Purchase #6	$244.39	13.348%	$277.0112	$277.01	$277.00	$277.00
Purchase #7	$231.52	11.812%	$258.8671	$258.87	$258.85	$258.90
7 purchase totals =	$1,390.62		$1,534.0481	$1,534.06	$1,533.95	$1,534.20