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	$113.46	11.225%	$126.1959	$126.20	$126.20	$126.20
Purchase #2	$250.92	5.367%	$264.3869	$264.39	$264.40	$264.40
Purchase #3	$94.59	9.264%	$103.3528	$103.35	$103.35	$103.40
Purchase #4	$50.41	9.838%	$55.3693	$55.37	$55.35	$55.40
Purchase #5	$130.36	3.455%	$134.8639	$134.86	$134.85	$134.90
Purchase #6	$42.64	7.721%	$45.9322	$45.93	$45.95	$45.90
Purchase #7	$154.26	12.378%	$173.3543	$173.35	$173.35	$173.40
7 purchase totals =	$836.64		$903.4553	$903.45	$903.45	$903.60