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	$69.88	3.808%	$72.541	$72.54	$72.55	$72.50
Purchase #2	$151.92	4.739%	$159.1195	$159.12	$159.10	$159.10
Purchase #3	$104.38	4.332%	$108.9017	$108.90	$108.90	$108.90
Purchase #4	$199.28	4.568%	$208.3831	$208.38	$208.40	$208.40
Purchase #5	$135.79	4.512%	$141.9168	$141.92	$141.90	$141.90
Purchase #6	$159.34	4.494%	$166.5007	$166.50	$166.50	$166.50
Purchase #7	$186.41	4.446%	$194.6978	$194.70	$194.70	$194.70
7 purchase totals =	$1,007.00		$1,052.0606	$1,052.06	$1,052.05	$1,052.00