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	$244.53	6.255%	$259.8254	$259.83	$259.85	$259.80
Purchase #2	$120.61	5.318%	$127.024	$127.02	$127.00	$127.00
Purchase #3	$244.98	4.161%	$255.1736	$255.17	$255.15	$255.20
Purchase #4	$237.89	11.112%	$264.3243	$264.32	$264.30	$264.30
Purchase #5	$59.75	9.776%	$65.5912	$65.59	$65.60	$65.60
Purchase #6	$156.75	3.702%	$162.5529	$162.55	$162.55	$162.60
Purchase #7	$228.43	7.662%	$245.9323	$245.93	$245.95	$245.90
7 purchase totals =	$1,292.94		$1,380.4237	$1,380.41	$1,380.40	$1,380.40