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	$60.48	8.657%	$65.7158	$65.72	$65.70	$65.70
Purchase #2	$164.76	5.764%	$174.2568	$174.26	$174.25	$174.30
Purchase #3	$194.47	11.814%	$217.4447	$217.44	$217.45	$217.40
Purchase #4	$111.32	11.183%	$123.7689	$123.77	$123.75	$123.80
Purchase #5	$128.71	7.150%	$137.9128	$137.91	$137.90	$137.90
Purchase #6	$139.58	4.511%	$145.8765	$145.88	$145.90	$145.90
Purchase #7	$97.60	11.872%	$109.1871	$109.19	$109.20	$109.20
7 purchase totals =	$896.92		$974.1626	$974.17	$974.15	$974.20