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	$142.56	5.687%	$150.6674	$150.67	$150.65	$150.70
Purchase #2	$148.79	6.347%	$158.2337	$158.23	$158.25	$158.20
Purchase #3	$97.82	13.653%	$111.1754	$111.18	$111.20	$111.20
Purchase #4	$101.37	3.516%	$104.9342	$104.93	$104.95	$104.90
Purchase #5	$19.44	5.601%	$20.5288	$20.53	$20.55	$20.50
Purchase #6	$238.73	11.566%	$266.3415	$266.34	$266.35	$266.30
Purchase #7	$157.80	10.601%	$174.5284	$174.53	$174.55	$174.50
7 purchase totals =	$906.51		$986.4094	$986.41	$986.50	$986.30