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	$89.69	11.194%	$99.7299	$99.73	$99.75	$99.70
Purchase #2	$205.40	6.318%	$218.3772	$218.38	$218.40	$218.40
Purchase #3	$99.76	9.467%	$109.2043	$109.20	$109.20	$109.20
Purchase #4	$206.34	6.867%	$220.5094	$220.51	$220.50	$220.50
Purchase #5	$75.70	8.813%	$82.3714	$82.37	$82.35	$82.40
Purchase #6	$126.44	8.414%	$137.0787	$137.08	$137.10	$137.10
Purchase #7	$152.46	8.566%	$165.5197	$165.52	$165.50	$165.50
7 purchase totals =	$955.79		$1,032.7906	$1,032.79	$1,032.80	$1,032.80