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	$43.73	11.633%	$48.8171	$48.82	$48.80	$48.80
Purchase #2	$191.40	11.327%	$213.0799	$213.08	$213.10	$213.10
Purchase #3	$188.86	9.151%	$206.1426	$206.14	$206.15	$206.10
Purchase #4	$117.64	4.872%	$123.3714	$123.37	$123.35	$123.40
Purchase #5	$203.73	12.784%	$229.7748	$229.77	$229.75	$229.80
Purchase #6	$142.73	7.590%	$153.5632	$153.56	$153.55	$153.60
Purchase #7	$170.50	8.598%	$185.1596	$185.16	$185.15	$185.20
7 purchase totals =	$1,058.59		$1,159.9086	$1,159.90	$1,159.85	$1,160.00