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	$162.42	3.347%	$167.8562	$167.86	$167.85	$167.90
Purchase #2	$83.39	8.683%	$90.6308	$90.63	$90.65	$90.60
Purchase #3	$102.31	7.457%	$109.9393	$109.94	$109.95	$109.90
Purchase #4	$122.76	7.460%	$131.9179	$131.92	$131.90	$131.90
Purchase #5	$53.72	11.481%	$59.8876	$59.89	$59.90	$59.90
Purchase #6	$210.77	3.823%	$218.8277	$218.83	$218.85	$218.80
Purchase #7	$5.79	8.418%	$6.2774	$6.28	$6.30	$6.30
7 purchase totals =	$741.16		$785.3369	$785.35	$785.40	$785.30