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	$101.62	5.582%	$107.2924	$107.29	$107.30	$107.30
Purchase #2	$70.54	10.140%	$77.6928	$77.69	$77.70	$77.70
Purchase #3	$40.86	5.717%	$43.196	$43.20	$43.20	$43.20
Purchase #4	$18.83	10.173%	$20.7456	$20.75	$20.75	$20.70
Purchase #5	$55.77	6.236%	$59.2478	$59.25	$59.25	$59.20
Purchase #6	$168.69	3.438%	$174.4896	$174.49	$174.50	$174.50
Purchase #7	$46.68	12.417%	$52.4763	$52.48	$52.50	$52.50
7 purchase totals =	$502.99		$535.1405	$535.15	$535.20	$535.10