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	$162.41	5.659%	$171.6008	$171.60	$171.60	$171.60
Purchase #2	$76.65	3.735%	$79.5129	$79.51	$79.50	$79.50
Purchase #3	$87.43	13.309%	$99.0661	$99.07	$99.05	$99.10
Purchase #4	$55.82	11.245%	$62.097	$62.10	$62.10	$62.10
Purchase #5	$216.27	6.472%	$230.267	$230.27	$230.25	$230.30
Purchase #6	$12.49	3.520%	$12.9296	$12.93	$12.95	$12.90
Purchase #7	$89.91	7.234%	$96.4141	$96.41	$96.40	$96.40
7 purchase totals =	$700.98		$751.8875	$751.89	$751.85	$751.90