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	$109.28	8.393%	$118.4519	$118.45	$118.45	$118.50
Purchase #2	$186.74	5.113%	$196.288	$196.29	$196.30	$196.30
Purchase #3	$171.49	7.377%	$184.1408	$184.14	$184.15	$184.10
Purchase #4	$99.72	3.302%	$103.0128	$103.01	$103.00	$103.00
Purchase #5	$18.43	9.198%	$20.1252	$20.13	$20.15	$20.10
Purchase #6	$231.93	6.621%	$247.2861	$247.29	$247.30	$247.30
Purchase #7	$246.81	9.708%	$270.7703	$270.77	$270.75	$270.80
7 purchase totals =	$1,064.40		$1,140.0751	$1,140.08	$1,140.10	$1,140.10