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	$57.98	7.450%	$62.2995	$62.30	$62.30	$62.30
Purchase #2	$48.62	7.614%	$52.3219	$52.32	$52.30	$52.30
Purchase #3	$97.66	12.222%	$109.596	$109.60	$109.60	$109.60
Purchase #4	$104.59	5.679%	$110.5297	$110.53	$110.55	$110.50
Purchase #5	$100.61	12.867%	$113.5555	$113.56	$113.55	$113.60
Purchase #6	$248.73	12.416%	$279.6123	$279.61	$279.60	$279.60
Purchase #7	$197.34	10.587%	$218.2324	$218.23	$218.25	$218.20
7 purchase totals =	$855.53		$946.1473	$946.15	$946.15	$946.10