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	$53.69	10.842%	$59.5111	$59.51	$59.50	$59.50
Purchase #2	$241.50	9.358%	$264.0996	$264.10	$264.10	$264.10
Purchase #3	$193.49	8.398%	$209.7393	$209.74	$209.75	$209.70
Purchase #4	$205.46	3.434%	$212.5155	$212.52	$212.50	$212.50
Purchase #5	$34.52	10.692%	$38.2109	$38.21	$38.20	$38.20
Purchase #6	$175.43	5.478%	$185.0401	$185.04	$185.05	$185.00
Purchase #7	$91.42	8.462%	$99.156	$99.16	$99.15	$99.20
7 purchase totals =	$995.51		$1,068.2725	$1,068.28	$1,068.25	$1,068.20