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	$67.61	8.312%	$73.2297	$73.23	$73.25	$73.20
Purchase #2	$60.52	11.492%	$67.475	$67.48	$67.50	$67.50
Purchase #3	$181.30	4.641%	$189.7141	$189.71	$189.70	$189.70
Purchase #4	$114.28	5.400%	$120.4511	$120.45	$120.45	$120.50
Purchase #5	$84.77	5.105%	$89.0975	$89.10	$89.10	$89.10
Purchase #6	$60.31	9.138%	$65.8211	$65.82	$65.80	$65.80
Purchase #7	$159.38	12.641%	$179.5272	$179.53	$179.55	$179.50
7 purchase totals =	$728.17		$785.3157	$785.32	$785.35	$785.30