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	$30.42	5.834%	$32.1947	$32.19	$32.20	$32.20
Purchase #2	$16.94	7.841%	$18.2683	$18.27	$18.25	$18.30
Purchase #3	$57.71	3.332%	$59.6329	$59.63	$59.65	$59.60
Purchase #4	$170.85	6.865%	$182.5789	$182.58	$182.60	$182.60
Purchase #5	$64.34	5.333%	$67.7713	$67.77	$67.75	$67.80
Purchase #6	$105.34	6.736%	$112.4357	$112.44	$112.45	$112.40
Purchase #7	$67.38	8.430%	$73.0601	$73.06	$73.05	$73.10
7 purchase totals =	$512.98		$545.9419	$545.94	$545.95	$546.00