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	$242.94	9.536%	$266.1068	$266.11	$266.10	$266.10
Purchase #2	$94.77	7.399%	$101.782	$101.78	$101.80	$101.80
Purchase #3	$85.38	8.603%	$92.7252	$92.73	$92.75	$92.70
Purchase #4	$216.99	7.566%	$233.4075	$233.41	$233.40	$233.40
Purchase #5	$82.47	3.442%	$85.3086	$85.31	$85.30	$85.30
Purchase #6	$197.35	3.430%	$204.1191	$204.12	$204.10	$204.10
Purchase #7	$191.59	11.442%	$213.5117	$213.51	$213.50	$213.50
7 purchase totals =	$1,111.49		$1,196.9609	$1,196.97	$1,196.95	$1,196.90