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	$210.48	13.374%	$238.6296	$238.63	$238.65	$238.60
Purchase #2	$221.46	11.696%	$247.362	$247.36	$247.35	$247.40
Purchase #3	$27.58	7.695%	$29.7023	$29.70	$29.70	$29.70
Purchase #4	$101.95	9.503%	$111.6383	$111.64	$111.65	$111.60
Purchase #5	$166.86	13.490%	$189.3694	$189.37	$189.35	$189.40
Purchase #6	$216.88	10.661%	$240.0016	$240.00	$240.00	$240.00
Purchase #7	$118.35	7.582%	$127.3233	$127.32	$127.30	$127.30
7 purchase totals =	$1,063.56		$1,184.0265	$1,184.02	$1,184.00	$1,184.00