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	$97.29	4.593%	$101.7585	$101.76	$101.75	$101.80
Purchase #2	$218.28	10.362%	$240.8982	$240.90	$240.90	$240.90
Purchase #3	$130.69	9.755%	$143.4388	$143.44	$143.45	$143.40
Purchase #4	$28.94	12.779%	$32.6382	$32.64	$32.65	$32.60
Purchase #5	$130.53	10.790%	$144.6142	$144.61	$144.60	$144.60
Purchase #6	$212.31	13.623%	$241.233	$241.23	$241.25	$241.20
Purchase #7	$106.47	6.237%	$113.1105	$113.11	$113.10	$113.10
7 purchase totals =	$924.51		$1,017.6914	$1,017.69	$1,017.70	$1,017.60