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	$42.54	9.224%	$46.4639	$46.46	$46.45	$46.50
Purchase #2	$38.53	11.753%	$43.0584	$43.06	$43.05	$43.10
Purchase #3	$138.33	4.333%	$144.3238	$144.32	$144.30	$144.30
Purchase #4	$209.25	6.444%	$222.7341	$222.73	$222.75	$222.70
Purchase #5	$92.59	11.384%	$103.1304	$103.13	$103.15	$103.10
Purchase #6	$190.69	5.174%	$200.5563	$200.56	$200.55	$200.60
Purchase #7	$184.37	10.832%	$204.341	$204.34	$204.35	$204.30
7 purchase totals =	$896.30		$964.6079	$964.60	$964.60	$964.60