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	$149.48	12.504%	$168.171	$168.17	$168.15	$168.20
Purchase #2	$196.80	4.646%	$205.9433	$205.94	$205.95	$205.90
Purchase #3	$238.42	9.581%	$261.263	$261.26	$261.25	$261.30
Purchase #4	$165.31	12.193%	$185.4662	$185.47	$185.45	$185.50
Purchase #5	$17.85	13.697%	$20.2949	$20.29	$20.30	$20.30
Purchase #6	$91.73	10.861%	$101.6928	$101.69	$101.70	$101.70
Purchase #7	$95.74	12.349%	$107.5629	$107.56	$107.55	$107.60
7 purchase totals =	$955.33		$1,050.3941	$1,050.38	$1,050.35	$1,050.50