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	$53.86	10.815%	$59.685	$59.69	$59.70	$59.70
Purchase #2	$49.87	4.792%	$52.2598	$52.26	$52.25	$52.30
Purchase #3	$191.67	10.755%	$212.2841	$212.28	$212.30	$212.30
Purchase #4	$47.43	13.704%	$53.9298	$53.93	$53.95	$53.90
Purchase #5	$185.42	7.518%	$199.3599	$199.36	$199.35	$199.40
Purchase #6	$142.88	5.693%	$151.0142	$151.01	$151.00	$151.00
Purchase #7	$35.90	6.559%	$38.2547	$38.25	$38.25	$38.30
7 purchase totals =	$707.03		$766.7875	$766.78	$766.80	$766.90