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	$100.25	9.185%	$109.458	$109.46	$109.45	$109.50
Purchase #2	$145.99	6.647%	$155.694	$155.69	$155.70	$155.70
Purchase #3	$28.93	10.836%	$32.0649	$32.06	$32.05	$32.10
Purchase #4	$127.74	13.614%	$145.1305	$145.13	$145.15	$145.10
Purchase #5	$116.30	4.348%	$121.3567	$121.36	$121.35	$121.40
Purchase #6	$189.55	3.614%	$196.4003	$196.40	$196.40	$196.40
Purchase #7	$54.56	4.555%	$57.0452	$57.05	$57.05	$57.00
7 purchase totals =	$763.32		$817.1496	$817.15	$817.15	$817.20