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	$150.56	10.137%	$165.8223	$165.82	$165.80	$165.80
Purchase #2	$169.56	9.599%	$185.8361	$185.84	$185.85	$185.80
Purchase #3	$100.40	4.356%	$104.7734	$104.77	$104.75	$104.80
Purchase #4	$226.72	4.358%	$236.6005	$236.60	$236.60	$236.60
Purchase #5	$207.53	12.155%	$232.7553	$232.76	$232.75	$232.80
Purchase #6	$89.39	13.583%	$101.5318	$101.53	$101.55	$101.50
Purchase #7	$73.43	3.823%	$76.2372	$76.24	$76.25	$76.20
7 purchase totals =	$1,017.59		$1,103.5566	$1,103.56	$1,103.55	$1,103.50