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	$42.85	9.486%	$46.9148	$46.91	$46.90	$46.90
Purchase #2	$118.69	11.155%	$131.9299	$131.93	$131.95	$131.90
Purchase #3	$203.26	8.483%	$220.5025	$220.50	$220.50	$220.50
Purchase #4	$29.46	12.608%	$33.1743	$33.17	$33.15	$33.20
Purchase #5	$233.38	10.843%	$258.6854	$258.69	$258.70	$258.70
Purchase #6	$131.83	4.688%	$138.0102	$138.01	$138.00	$138.00
Purchase #7	$152.73	13.511%	$173.3654	$173.37	$173.35	$173.40
7 purchase totals =	$912.20		$1,002.5825	$1,002.58	$1,002.55	$1,002.60