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	$246.65	7.692%	$265.6223	$265.62	$265.60	$265.60
Purchase #2	$91.49	10.145%	$100.7717	$100.77	$100.75	$100.80
Purchase #3	$19.41	7.453%	$20.8566	$20.86	$20.85	$20.90
Purchase #4	$14.28	7.701%	$15.3797	$15.38	$15.40	$15.40
Purchase #5	$174.76	12.575%	$196.7361	$196.74	$196.75	$196.70
Purchase #6	$185.62	9.694%	$203.614	$203.61	$203.60	$203.60
Purchase #7	$49.61	6.151%	$52.6615	$52.66	$52.65	$52.70
7 purchase totals =	$781.82		$855.6419	$855.64	$855.60	$855.70