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	$96.86	3.623%	$100.3692	$100.37	$100.35	$100.40
Purchase #2	$33.70	12.433%	$37.8899	$37.89	$37.90	$37.90
Purchase #3	$250.66	10.278%	$276.4228	$276.42	$276.40	$276.40
Purchase #4	$236.72	5.783%	$250.4095	$250.41	$250.40	$250.40
Purchase #5	$220.28	6.472%	$234.5365	$234.54	$234.55	$234.50
Purchase #6	$171.46	6.173%	$182.0442	$182.04	$182.05	$182.00
Purchase #7	$199.91	3.262%	$206.4311	$206.43	$206.45	$206.40
7 purchase totals =	$1,209.59		$1,288.1032	$1,288.10	$1,288.10	$1,288.00