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	$157.26	7.180%	$168.5513	$168.55	$168.55	$168.60
Purchase #2	$91.57	8.417%	$99.2774	$99.28	$99.30	$99.30
Purchase #3	$139.46	3.356%	$144.1403	$144.14	$144.15	$144.10
Purchase #4	$136.46	4.680%	$142.8463	$142.85	$142.85	$142.80
Purchase #5	$104.38	6.669%	$111.3411	$111.34	$111.35	$111.30
Purchase #6	$95.36	12.485%	$107.2657	$107.27	$107.25	$107.30
Purchase #7	$143.37	4.220%	$149.4202	$149.42	$149.40	$149.40
7 purchase totals =	$867.86		$922.8423	$922.85	$922.85	$922.80