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	$148.47	5.601%	$156.7858	$156.79	$156.80	$156.80
Purchase #2	$156.68	9.277%	$171.2152	$171.22	$171.20	$171.20
Purchase #3	$204.70	8.237%	$221.5611	$221.56	$221.55	$221.60
Purchase #4	$51.63	9.760%	$56.6691	$56.67	$56.65	$56.70
Purchase #5	$188.30	4.289%	$196.3762	$196.38	$196.40	$196.40
Purchase #6	$196.76	4.714%	$206.0353	$206.04	$206.05	$206.00
Purchase #7	$133.32	6.767%	$142.3418	$142.34	$142.35	$142.30
7 purchase totals =	$1,079.86		$1,150.9845	$1,151.00	$1,151.00	$1,151.00