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	$43.77	3.714%	$45.3956	$45.40	$45.40	$45.40
Purchase #2	$170.47	3.483%	$176.4075	$176.41	$176.40	$176.40
Purchase #3	$220.31	3.594%	$228.2279	$228.23	$228.25	$228.20
Purchase #4	$20.83	3.607%	$21.5813	$21.58	$21.60	$21.60
Purchase #5	$44.82	6.549%	$47.7553	$47.76	$47.75	$47.80
Purchase #6	$189.39	5.824%	$200.4201	$200.42	$200.40	$200.40
Purchase #7	$18.26	11.492%	$20.3584	$20.36	$20.35	$20.40
7 purchase totals =	$707.85		$740.1461	$740.16	$740.15	$740.20