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	$227.39	10.446%	$251.1432	$251.14	$251.15	$251.10
Purchase #2	$78.85	13.563%	$89.5444	$89.54	$89.55	$89.50
Purchase #3	$189.38	12.768%	$213.56	$213.56	$213.55	$213.60
Purchase #4	$231.54	6.453%	$246.4813	$246.48	$246.50	$246.50
Purchase #5	$54.27	7.482%	$58.3305	$58.33	$58.35	$58.30
Purchase #6	$187.27	6.199%	$198.8789	$198.88	$198.90	$198.90
Purchase #7	$224.96	13.849%	$256.1147	$256.11	$256.10	$256.10
7 purchase totals =	$1,193.66		$1,314.0530	$1,314.04	$1,314.10	$1,314.00