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	$70.26	3.244%	$72.5392	$72.54	$72.55	$72.50
Purchase #2	$107.73	3.329%	$111.3163	$111.32	$111.30	$111.30
Purchase #3	$124.72	6.830%	$133.2384	$133.24	$133.25	$133.20
Purchase #4	$212.25	5.253%	$223.3995	$223.40	$223.40	$223.40
Purchase #5	$201.71	5.670%	$213.147	$213.15	$213.15	$213.10
Purchase #6	$13.64	10.593%	$15.0849	$15.08	$15.10	$15.10
Purchase #7	$11.35	13.129%	$12.8401	$12.84	$12.85	$12.80
7 purchase totals =	$741.66		$781.5654	$781.57	$781.60	$781.40