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	$50.58	4.166%	$52.6872	$52.69	$52.70	$52.70
Purchase #2	$118.63	12.241%	$133.1515	$133.15	$133.15	$133.20
Purchase #3	$235.79	8.368%	$255.5209	$255.52	$255.50	$255.50
Purchase #4	$49.68	5.661%	$52.4924	$52.49	$52.50	$52.50
Purchase #5	$18.57	9.398%	$20.3152	$20.32	$20.30	$20.30
Purchase #6	$75.84	12.839%	$85.5771	$85.58	$85.60	$85.60
Purchase #7	$12.68	12.734%	$14.2947	$14.29	$14.30	$14.30
7 purchase totals =	$561.77		$614.0390	$614.04	$614.05	$614.10