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	$127.47	4.590%	$133.3209	$133.32	$133.30	$133.30
Purchase #2	$49.49	7.690%	$53.2958	$53.30	$53.30	$53.30
Purchase #3	$105.35	8.130%	$113.915	$113.92	$113.90	$113.90
Purchase #4	$71.63	3.307%	$73.9988	$74.00	$74.00	$74.00
Purchase #5	$76.83	7.486%	$82.5815	$82.58	$82.60	$82.60
Purchase #6	$55.32	10.801%	$61.2951	$61.30	$61.30	$61.30
Purchase #7	$100.70	8.279%	$109.037	$109.04	$109.05	$109.00
7 purchase totals =	$586.79		$627.4441	$627.46	$627.45	$627.40