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	$5.76	8.698%	$6.261	$6.26	$6.25	$6.30
Purchase #2	$238.25	6.869%	$254.6154	$254.62	$254.60	$254.60
Purchase #3	$38.83	7.107%	$41.5896	$41.59	$41.60	$41.60
Purchase #4	$49.47	10.335%	$54.5827	$54.58	$54.60	$54.60
Purchase #5	$126.70	12.208%	$142.1675	$142.17	$142.15	$142.20
Purchase #6	$239.65	4.391%	$250.173	$250.17	$250.15	$250.20
Purchase #7	$110.28	11.769%	$123.2589	$123.26	$123.25	$123.30
7 purchase totals =	$808.94		$872.6481	$872.65	$872.60	$872.80