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	$194.76	8.108%	$210.5511	$210.55	$210.55	$210.60
Purchase #2	$138.25	5.788%	$146.2519	$146.25	$146.25	$146.30
Purchase #3	$183.85	4.112%	$191.4099	$191.41	$191.40	$191.40
Purchase #4	$102.45	5.733%	$108.3235	$108.32	$108.30	$108.30
Purchase #5	$214.80	3.679%	$222.7025	$222.70	$222.70	$222.70
Purchase #6	$73.78	11.112%	$81.9784	$81.98	$82.00	$82.00
Purchase #7	$63.31	12.772%	$71.396	$71.40	$71.40	$71.40
7 purchase totals =	$971.20		$1,032.6133	$1,032.61	$1,032.60	$1,032.70