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	$52.88	11.814%	$59.1272	$59.13	$59.15	$59.10
Purchase #2	$16.85	3.158%	$17.3821	$17.38	$17.40	$17.40
Purchase #3	$78.27	13.468%	$88.8114	$88.81	$88.80	$88.80
Purchase #4	$43.35	8.641%	$47.0959	$47.10	$47.10	$47.10
Purchase #5	$22.95	13.753%	$26.1063	$26.11	$26.10	$26.10
Purchase #6	$106.39	5.115%	$111.8318	$111.83	$111.85	$111.80
Purchase #7	$245.67	8.642%	$266.9008	$266.90	$266.90	$266.90
7 purchase totals =	$566.36		$617.2555	$617.26	$617.30	$617.20