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	$57.98	11.333%	$64.5509	$64.55	$64.55	$64.60
Purchase #2	$185.78	8.208%	$201.0288	$201.03	$201.05	$201.00
Purchase #3	$43.50	12.170%	$48.794	$48.79	$48.80	$48.80
Purchase #4	$175.46	4.244%	$182.9065	$182.91	$182.90	$182.90
Purchase #5	$247.51	13.236%	$280.2704	$280.27	$280.25	$280.30
Purchase #6	$96.43	8.206%	$104.343	$104.34	$104.35	$104.30
Purchase #7	$117.71	4.851%	$123.4201	$123.42	$123.40	$123.40
7 purchase totals =	$924.37		$1,005.3137	$1,005.31	$1,005.30	$1,005.30