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	$210.30	7.334%	$225.7234	$225.72	$225.70	$225.70
Purchase #2	$98.86	5.155%	$103.9562	$103.96	$103.95	$104.00
Purchase #3	$205.85	3.450%	$212.9518	$212.95	$212.95	$213.00
Purchase #4	$41.63	10.240%	$45.8929	$45.89	$45.90	$45.90
Purchase #5	$11.73	4.416%	$12.248	$12.25	$12.25	$12.20
Purchase #6	$205.83	3.843%	$213.74	$213.74	$213.75	$213.70
Purchase #7	$120.86	5.595%	$127.6221	$127.62	$127.60	$127.60
7 purchase totals =	$895.06		$942.1344	$942.13	$942.10	$942.10