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	$127.45	11.486%	$142.0889	$142.09	$142.10	$142.10
Purchase #2	$157.51	4.132%	$164.0183	$164.02	$164.00	$164.00
Purchase #3	$147.77	13.827%	$168.2022	$168.20	$168.20	$168.20
Purchase #4	$195.83	13.813%	$222.88	$222.88	$222.90	$222.90
Purchase #5	$116.35	11.732%	$130.0002	$130.00	$130.00	$130.00
Purchase #6	$181.66	12.663%	$204.6636	$204.66	$204.65	$204.70
Purchase #7	$78.58	13.416%	$89.1223	$89.12	$89.10	$89.10
7 purchase totals =	$1,005.15		$1,120.9755	$1,120.97	$1,120.95	$1,121.00