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	$187.83	8.281%	$203.3842	$203.38	$203.40	$203.40
Purchase #2	$97.85	11.564%	$109.1654	$109.17	$109.15	$109.20
Purchase #3	$49.33	9.458%	$53.9956	$54.00	$54.00	$54.00
Purchase #4	$83.98	6.657%	$89.5705	$89.57	$89.55	$89.60
Purchase #5	$92.66	8.715%	$100.7353	$100.74	$100.75	$100.70
Purchase #6	$164.60	5.476%	$173.6135	$173.61	$173.60	$173.60
Purchase #7	$10.57	8.361%	$11.4538	$11.45	$11.45	$11.50
7 purchase totals =	$686.82		$741.9183	$741.92	$741.90	$742.00