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	$35.79	4.460%	$37.3862	$37.39	$37.40	$37.40
Purchase #2	$101.90	6.255%	$108.2738	$108.27	$108.25	$108.30
Purchase #3	$19.69	6.184%	$20.9076	$20.91	$20.90	$20.90
Purchase #4	$138.70	7.596%	$149.2357	$149.24	$149.25	$149.20
Purchase #5	$204.56	6.326%	$217.5005	$217.50	$217.50	$217.50
Purchase #6	$209.43	13.671%	$238.0612	$238.06	$238.05	$238.10
Purchase #7	$218.48	11.757%	$244.1667	$244.17	$244.15	$244.20
7 purchase totals =	$928.55		$1,015.5317	$1,015.54	$1,015.50	$1,015.60