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	$83.98	10.458%	$92.7626	$92.76	$92.75	$92.80
Purchase #2	$46.41	7.871%	$50.0629	$50.06	$50.05	$50.10
Purchase #3	$29.82	11.387%	$33.2156	$33.22	$33.20	$33.20
Purchase #4	$239.95	4.215%	$250.0639	$250.06	$250.05	$250.10
Purchase #5	$74.59	9.811%	$81.908	$81.91	$81.90	$81.90
Purchase #6	$68.42	5.871%	$72.4369	$72.44	$72.45	$72.40
Purchase #7	$139.64	8.418%	$151.3949	$151.39	$151.40	$151.40
7 purchase totals =	$682.81		$731.8448	$731.84	$731.80	$731.90