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	$147.73	9.627%	$161.952	$161.95	$161.95	$162.00
Purchase #2	$49.36	6.852%	$52.7421	$52.74	$52.75	$52.70
Purchase #3	$69.32	13.148%	$78.4342	$78.43	$78.45	$78.40
Purchase #4	$136.54	6.370%	$145.2376	$145.24	$145.25	$145.20
Purchase #5	$154.51	7.253%	$165.7166	$165.72	$165.70	$165.70
Purchase #6	$203.27	9.332%	$222.2392	$222.24	$222.25	$222.20
Purchase #7	$29.71	13.274%	$33.6537	$33.65	$33.65	$33.70
7 purchase totals =	$790.44		$859.9754	$859.97	$860.00	$859.90