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	$82.51	10.752%	$91.3815	$91.38	$91.40	$91.40
Purchase #2	$152.42	12.602%	$171.628	$171.63	$171.65	$171.60
Purchase #3	$196.74	13.284%	$222.8749	$222.87	$222.85	$222.90
Purchase #4	$12.46	4.484%	$13.0187	$13.02	$13.00	$13.00
Purchase #5	$179.81	7.804%	$193.8424	$193.84	$193.85	$193.80
Purchase #6	$159.49	8.146%	$172.4821	$172.48	$172.50	$172.50
Purchase #7	$136.87	7.463%	$147.0846	$147.08	$147.10	$147.10
7 purchase totals =	$920.30		$1,012.3122	$1,012.30	$1,012.35	$1,012.30