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	$44.74	3.397%	$46.2598	$46.26	$46.25	$46.30
Purchase #2	$52.93	3.640%	$54.8567	$54.86	$54.85	$54.90
Purchase #3	$108.30	13.628%	$123.0591	$123.06	$123.05	$123.10
Purchase #4	$125.32	13.425%	$142.1442	$142.14	$142.15	$142.10
Purchase #5	$147.86	13.845%	$168.3312	$168.33	$168.35	$168.30
Purchase #6	$48.40	11.131%	$53.7874	$53.79	$53.80	$53.80
Purchase #7	$171.73	13.330%	$194.6216	$194.62	$194.60	$194.60
7 purchase totals =	$699.28		$783.0600	$783.06	$783.05	$783.10