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	$95.30	4.325%	$99.4217	$99.42	$99.40	$99.40
Purchase #2	$165.89	7.756%	$178.7564	$178.76	$178.75	$178.80
Purchase #3	$57.65	5.307%	$60.7095	$60.71	$60.70	$60.70
Purchase #4	$85.36	3.676%	$88.4978	$88.50	$88.50	$88.50
Purchase #5	$195.55	5.664%	$206.626	$206.63	$206.65	$206.60
Purchase #6	$83.32	13.440%	$94.5182	$94.52	$94.50	$94.50
Purchase #7	$138.82	9.435%	$151.9177	$151.92	$151.90	$151.90
7 purchase totals =	$821.89		$880.4473	$880.46	$880.40	$880.40