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	$105.91	12.238%	$118.8713	$118.87	$118.85	$118.90
Purchase #2	$50.76	5.677%	$53.6416	$53.64	$53.65	$53.60
Purchase #3	$233.80	4.637%	$244.6413	$244.64	$244.65	$244.60
Purchase #4	$179.32	11.825%	$200.5246	$200.52	$200.50	$200.50
Purchase #5	$150.60	4.377%	$157.1918	$157.19	$157.20	$157.20
Purchase #6	$157.63	10.706%	$174.5059	$174.51	$174.50	$174.50
Purchase #7	$140.73	5.372%	$148.29	$148.29	$148.30	$148.30
7 purchase totals =	$1,018.75		$1,097.6665	$1,097.66	$1,097.65	$1,097.60