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	$179.70	6.317%	$191.0516	$191.05	$191.05	$191.10
Purchase #2	$85.56	4.275%	$89.2177	$89.22	$89.20	$89.20
Purchase #3	$27.45	10.821%	$30.4204	$30.42	$30.40	$30.40
Purchase #4	$205.62	6.766%	$219.5322	$219.53	$219.55	$219.50
Purchase #5	$171.59	4.469%	$179.2584	$179.26	$179.25	$179.30
Purchase #6	$214.81	13.769%	$244.3872	$244.39	$244.40	$244.40
Purchase #7	$121.41	13.566%	$137.8805	$137.88	$137.90	$137.90
7 purchase totals =	$1,006.14		$1,091.7480	$1,091.75	$1,091.75	$1,091.80