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	$204.38	6.465%	$217.5932	$217.59	$217.60	$217.60
Purchase #2	$53.42	6.253%	$56.7604	$56.76	$56.75	$56.80
Purchase #3	$223.54	7.589%	$240.5045	$240.50	$240.50	$240.50
Purchase #4	$169.91	5.758%	$179.6934	$179.69	$179.70	$179.70
Purchase #5	$80.35	11.360%	$89.4778	$89.48	$89.50	$89.50
Purchase #6	$146.82	4.506%	$153.4357	$153.44	$153.45	$153.40
Purchase #7	$46.76	5.746%	$49.4468	$49.45	$49.45	$49.40
7 purchase totals =	$925.18		$986.9118	$986.91	$986.95	$986.90