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	$191.46	10.120%	$210.8358	$210.84	$210.85	$210.80
Purchase #2	$191.77	12.518%	$215.7758	$215.78	$215.80	$215.80
Purchase #3	$55.83	11.580%	$62.2951	$62.30	$62.30	$62.30
Purchase #4	$48.60	5.802%	$51.4198	$51.42	$51.40	$51.40
Purchase #5	$65.93	11.427%	$73.4638	$73.46	$73.45	$73.50
Purchase #6	$226.78	5.209%	$238.593	$238.59	$238.60	$238.60
Purchase #7	$170.64	8.813%	$185.6785	$185.68	$185.70	$185.70
7 purchase totals =	$951.01		$1,038.0618	$1,038.07	$1,038.10	$1,038.10