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	$172.73	10.870%	$191.5058	$191.51	$191.50	$191.50
Purchase #2	$112.55	6.456%	$119.8162	$119.82	$119.80	$119.80
Purchase #3	$42.58	8.536%	$46.2146	$46.21	$46.20	$46.20
Purchase #4	$120.76	6.240%	$128.2954	$128.30	$128.30	$128.30
Purchase #5	$220.74	11.183%	$245.4254	$245.43	$245.45	$245.40
Purchase #6	$93.25	8.580%	$101.2509	$101.25	$101.25	$101.30
Purchase #7	$116.98	12.743%	$131.8868	$131.89	$131.90	$131.90
7 purchase totals =	$879.59		$964.3951	$964.41	$964.40	$964.40