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	$169.54	12.489%	$190.7139	$190.71	$190.70	$190.70
Purchase #2	$87.90	11.417%	$97.9355	$97.94	$97.95	$97.90
Purchase #3	$185.73	5.654%	$196.2312	$196.23	$196.25	$196.20
Purchase #4	$85.49	13.181%	$96.7584	$96.76	$96.75	$96.80
Purchase #5	$207.71	7.292%	$222.8562	$222.86	$222.85	$222.90
Purchase #6	$201.40	9.294%	$220.1181	$220.12	$220.10	$220.10
Purchase #7	$138.46	9.686%	$151.8712	$151.87	$151.85	$151.90
7 purchase totals =	$1,076.23		$1,176.4845	$1,176.49	$1,176.45	$1,176.50