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	$96.43	4.251%	$100.5292	$100.53	$100.55	$100.50
Purchase #2	$128.66	7.503%	$138.3134	$138.31	$138.30	$138.30
Purchase #3	$170.67	5.705%	$180.4067	$180.41	$180.40	$180.40
Purchase #4	$245.56	5.687%	$259.525	$259.53	$259.55	$259.50
Purchase #5	$120.43	10.385%	$132.9367	$132.94	$132.95	$132.90
Purchase #6	$136.70	13.217%	$154.7676	$154.77	$154.75	$154.80
Purchase #7	$78.35	12.732%	$88.3255	$88.33	$88.35	$88.30
7 purchase totals =	$976.80		$1,054.8041	$1,054.82	$1,054.85	$1,054.70