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	$227.94	12.374%	$256.1453	$256.15	$256.15	$256.10
Purchase #2	$56.86	4.857%	$59.6217	$59.62	$59.60	$59.60
Purchase #3	$203.37	4.376%	$212.2695	$212.27	$212.25	$212.30
Purchase #4	$151.32	4.308%	$157.8389	$157.84	$157.85	$157.80
Purchase #5	$160.56	13.518%	$182.2645	$182.26	$182.25	$182.30
Purchase #6	$170.36	12.278%	$191.2768	$191.28	$191.30	$191.30
Purchase #7	$12.36	3.279%	$12.7653	$12.77	$12.75	$12.80
7 purchase totals =	$982.77		$1,072.1820	$1,072.19	$1,072.15	$1,072.20