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	$68.88	3.216%	$71.0952	$71.10	$71.10	$71.10
Purchase #2	$20.87	6.515%	$22.2297	$22.23	$22.25	$22.20
Purchase #3	$82.76	3.283%	$85.477	$85.48	$85.50	$85.50
Purchase #4	$132.79	5.829%	$140.5303	$140.53	$140.55	$140.50
Purchase #5	$105.95	6.251%	$112.5729	$112.57	$112.55	$112.60
Purchase #6	$15.78	10.789%	$17.4825	$17.48	$17.50	$17.50
Purchase #7	$52.89	11.687%	$59.0713	$59.07	$59.05	$59.10
7 purchase totals =	$479.92		$508.4589	$508.46	$508.50	$508.50