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	$32.73	3.722%	$33.9482	$33.95	$33.95	$33.90
Purchase #2	$166.46	13.297%	$188.5942	$188.59	$188.60	$188.60
Purchase #3	$48.87	5.599%	$51.6062	$51.61	$51.60	$51.60
Purchase #4	$88.92	10.187%	$97.9783	$97.98	$98.00	$98.00
Purchase #5	$29.44	11.229%	$32.7458	$32.75	$32.75	$32.70
Purchase #6	$30.76	5.873%	$32.5665	$32.57	$32.55	$32.60
Purchase #7	$91.61	4.804%	$96.0109	$96.01	$96.00	$96.00
7 purchase totals =	$488.79		$533.4501	$533.46	$533.45	$533.40