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	$191.58	6.706%	$204.4274	$204.43	$204.45	$204.40
Purchase #2	$249.96	6.367%	$265.875	$265.88	$265.90	$265.90
Purchase #3	$90.31	10.617%	$99.8982	$99.90	$99.90	$99.90
Purchase #4	$57.57	3.405%	$59.5303	$59.53	$59.55	$59.50
Purchase #5	$25.38	6.265%	$26.9701	$26.97	$26.95	$27.00
Purchase #6	$43.70	9.342%	$47.7825	$47.78	$47.80	$47.80
Purchase #7	$35.83	3.842%	$37.2066	$37.21	$37.20	$37.20
7 purchase totals =	$694.33		$741.6901	$741.70	$741.75	$741.70