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	$140.46	4.447%	$146.7063	$146.71	$146.70	$146.70
Purchase #2	$88.56	10.857%	$98.175	$98.18	$98.20	$98.20
Purchase #3	$105.29	12.219%	$118.1554	$118.16	$118.15	$118.20
Purchase #4	$242.86	4.632%	$254.1093	$254.11	$254.10	$254.10
Purchase #5	$178.80	4.538%	$186.9139	$186.91	$186.90	$186.90
Purchase #6	$117.95	8.147%	$127.5594	$127.56	$127.55	$127.60
Purchase #7	$99.83	9.234%	$109.0483	$109.05	$109.05	$109.00
7 purchase totals =	$973.75		$1,040.6676	$1,040.68	$1,040.65	$1,040.70