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	$40.72	6.402%	$43.3269	$43.33	$43.35	$43.30
Purchase #2	$116.84	3.428%	$120.8453	$120.85	$120.85	$120.80
Purchase #3	$209.75	6.315%	$222.9957	$223.00	$223.00	$223.00
Purchase #4	$9.86	8.400%	$10.6882	$10.69	$10.70	$10.70
Purchase #5	$96.76	13.456%	$109.78	$109.78	$109.80	$109.80
Purchase #6	$229.44	11.508%	$255.844	$255.84	$255.85	$255.80
Purchase #7	$181.45	12.813%	$204.6992	$204.70	$204.70	$204.70
7 purchase totals =	$884.82		$968.1793	$968.19	$968.25	$968.10