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	$202.72	5.221%	$213.304	$213.30	$213.30	$213.30
Purchase #2	$46.28	4.315%	$48.277	$48.28	$48.30	$48.30
Purchase #3	$166.61	7.867%	$179.7172	$179.72	$179.70	$179.70
Purchase #4	$154.89	11.320%	$172.4235	$172.42	$172.40	$172.40
Purchase #5	$231.78	4.207%	$241.531	$241.53	$241.55	$241.50
Purchase #6	$16.64	8.625%	$18.0752	$18.08	$18.10	$18.10
Purchase #7	$120.62	11.556%	$134.5588	$134.56	$134.55	$134.60
7 purchase totals =	$939.54		$1,007.8867	$1,007.89	$1,007.90	$1,007.90