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	$223.94	4.209%	$233.3656	$233.37	$233.35	$233.40
Purchase #2	$75.47	5.282%	$79.4563	$79.46	$79.45	$79.50
Purchase #3	$65.69	9.408%	$71.8701	$71.87	$71.85	$71.90
Purchase #4	$25.97	12.374%	$29.1835	$29.18	$29.20	$29.20
Purchase #5	$155.73	5.753%	$164.6891	$164.69	$164.70	$164.70
Purchase #6	$88.48	3.864%	$91.8989	$91.90	$91.90	$91.90
Purchase #7	$174.50	9.357%	$190.828	$190.83	$190.85	$190.80
7 purchase totals =	$809.78		$861.2915	$861.30	$861.30	$861.40