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	$45.37	6.578%	$48.3544	$48.35	$48.35	$48.40
Purchase #2	$81.69	5.712%	$86.3561	$86.36	$86.35	$86.40
Purchase #3	$166.99	10.642%	$184.7611	$184.76	$184.75	$184.80
Purchase #4	$18.60	9.174%	$20.3064	$20.31	$20.30	$20.30
Purchase #5	$96.75	3.725%	$100.3539	$100.35	$100.35	$100.40
Purchase #6	$53.45	4.413%	$55.8087	$55.81	$55.80	$55.80
Purchase #7	$185.50	5.689%	$196.0531	$196.05	$196.05	$196.10
7 purchase totals =	$648.35		$691.9937	$691.99	$691.95	$692.20