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	$71.47	9.309%	$78.1231	$78.12	$78.10	$78.10
Purchase #2	$186.27	13.277%	$211.0011	$211.00	$211.00	$211.00
Purchase #3	$247.48	8.479%	$268.4638	$268.46	$268.45	$268.50
Purchase #4	$245.72	3.764%	$254.9689	$254.97	$254.95	$255.00
Purchase #5	$110.62	7.579%	$119.0039	$119.00	$119.00	$119.00
Purchase #6	$173.33	13.213%	$196.2321	$196.23	$196.25	$196.20
Purchase #7	$122.96	3.575%	$127.3558	$127.36	$127.35	$127.40
7 purchase totals =	$1,157.85		$1,255.1487	$1,255.14	$1,255.10	$1,255.20