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	$33.27	13.635%	$37.8064	$37.81	$37.80	$37.80
Purchase #2	$135.78	6.801%	$145.0144	$145.01	$145.00	$145.00
Purchase #3	$72.50	6.496%	$77.2096	$77.21	$77.20	$77.20
Purchase #4	$248.80	8.184%	$269.1618	$269.16	$269.15	$269.20
Purchase #5	$160.86	11.474%	$179.3171	$179.32	$179.30	$179.30
Purchase #6	$141.90	11.254%	$157.8694	$157.87	$157.85	$157.90
Purchase #7	$159.91	3.814%	$166.009	$166.01	$166.00	$166.00
7 purchase totals =	$953.02		$1,032.3877	$1,032.39	$1,032.30	$1,032.40