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	$69.47	4.514%	$72.6059	$72.61	$72.60	$72.60
Purchase #2	$65.98	11.761%	$73.7399	$73.74	$73.75	$73.70
Purchase #3	$7.34	4.438%	$7.6657	$7.67	$7.65	$7.70
Purchase #4	$118.69	3.871%	$123.2845	$123.28	$123.30	$123.30
Purchase #5	$249.30	10.438%	$275.3219	$275.32	$275.30	$275.30
Purchase #6	$180.57	4.668%	$188.999	$189.00	$189.00	$189.00
Purchase #7	$50.43	4.618%	$52.7589	$52.76	$52.75	$52.80
7 purchase totals =	$741.78		$794.3758	$794.38	$794.35	$794.40