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	$105.87	6.200%	$112.4339	$112.43	$112.45	$112.40
Purchase #2	$161.25	6.855%	$172.3037	$172.30	$172.30	$172.30
Purchase #3	$48.72	3.148%	$50.2537	$50.25	$50.25	$50.30
Purchase #4	$14.39	10.195%	$15.8571	$15.86	$15.85	$15.90
Purchase #5	$191.67	3.437%	$198.2577	$198.26	$198.25	$198.30
Purchase #6	$138.67	6.860%	$148.1828	$148.18	$148.20	$148.20
Purchase #7	$98.69	4.374%	$103.0067	$103.01	$103.00	$103.00
7 purchase totals =	$759.26		$800.2956	$800.29	$800.30	$800.40