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	$61.94	3.430%	$64.0645	$64.06	$64.05	$64.10
Purchase #2	$90.45	3.172%	$93.3191	$93.32	$93.30	$93.30
Purchase #3	$33.83	13.668%	$38.4539	$38.45	$38.45	$38.50
Purchase #4	$187.73	6.409%	$199.7616	$199.76	$199.75	$199.80
Purchase #5	$179.30	9.482%	$196.3012	$196.30	$196.30	$196.30
Purchase #6	$37.39	10.767%	$41.4158	$41.42	$41.40	$41.40
Purchase #7	$96.83	13.641%	$110.0386	$110.04	$110.05	$110.00
7 purchase totals =	$687.47		$743.3547	$743.35	$743.30	$743.40