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	$28.52	6.795%	$30.4579	$30.46	$30.45	$30.50
Purchase #2	$53.92	10.727%	$59.704	$59.70	$59.70	$59.70
Purchase #3	$57.25	12.666%	$64.5013	$64.50	$64.50	$64.50
Purchase #4	$35.70	10.254%	$39.3607	$39.36	$39.35	$39.40
Purchase #5	$53.78	10.818%	$59.5979	$59.60	$59.60	$59.60
Purchase #6	$82.95	7.344%	$89.0418	$89.04	$89.05	$89.00
Purchase #7	$31.35	5.275%	$33.0037	$33.00	$33.00	$33.00
7 purchase totals =	$343.47		$375.6673	$375.66	$375.65	$375.70