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	$46.46	3.376%	$48.0285	$48.03	$48.05	$48.00
Purchase #2	$78.34	12.864%	$88.4177	$88.42	$88.40	$88.40
Purchase #3	$179.74	11.764%	$200.8846	$200.88	$200.90	$200.90
Purchase #4	$56.76	10.767%	$62.8713	$62.87	$62.85	$62.90
Purchase #5	$92.82	4.874%	$97.344	$97.34	$97.35	$97.30
Purchase #6	$89.69	11.392%	$99.9075	$99.91	$99.90	$99.90
Purchase #7	$120.89	8.800%	$131.5283	$131.53	$131.55	$131.50
7 purchase totals =	$664.70		$728.9819	$728.98	$729.00	$728.90