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	$237.69	9.858%	$261.1215	$261.12	$261.10	$261.10
Purchase #2	$181.78	8.219%	$196.7205	$196.72	$196.70	$196.70
Purchase #3	$88.68	3.830%	$92.0764	$92.08	$92.10	$92.10
Purchase #4	$101.75	7.631%	$109.5145	$109.51	$109.50	$109.50
Purchase #5	$225.93	12.676%	$254.5689	$254.57	$254.55	$254.60
Purchase #6	$147.58	6.204%	$156.7359	$156.74	$156.75	$156.70
Purchase #7	$53.76	3.131%	$55.4432	$55.44	$55.45	$55.40
7 purchase totals =	$1,037.17		$1,126.1809	$1,126.18	$1,126.15	$1,126.10