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	$62.62	13.829%	$71.2797	$71.28	$71.30	$71.30
Purchase #2	$221.45	3.254%	$228.656	$228.66	$228.65	$228.70
Purchase #3	$75.44	3.250%	$77.8918	$77.89	$77.90	$77.90
Purchase #4	$168.28	11.440%	$187.5312	$187.53	$187.55	$187.50
Purchase #5	$78.79	8.635%	$85.5935	$85.59	$85.60	$85.60
Purchase #6	$17.93	13.448%	$20.3412	$20.34	$20.35	$20.30
Purchase #7	$105.63	5.502%	$111.4418	$111.44	$111.45	$111.40
7 purchase totals =	$730.14		$782.7352	$782.73	$782.80	$782.70