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	$141.69	5.430%	$149.3838	$149.38	$149.40	$149.40
Purchase #2	$221.55	5.430%	$233.5802	$233.58	$233.60	$233.60
Purchase #3	$82.55	3.242%	$85.2263	$85.23	$85.25	$85.20
Purchase #4	$125.79	12.235%	$141.1804	$141.18	$141.20	$141.20
Purchase #5	$46.87	12.586%	$52.7691	$52.77	$52.75	$52.80
Purchase #6	$98.42	11.174%	$109.4175	$109.42	$109.40	$109.40
Purchase #7	$24.29	6.690%	$25.915	$25.92	$25.90	$25.90
7 purchase totals =	$741.16		$797.4723	$797.48	$797.50	$797.50