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	$166.41	5.829%	$176.11	$176.11	$176.10	$176.10
Purchase #2	$234.65	6.691%	$250.3504	$250.35	$250.35	$250.40
Purchase #3	$111.33	3.291%	$114.9939	$114.99	$115.00	$115.00
Purchase #4	$61.32	13.213%	$69.4222	$69.42	$69.40	$69.40
Purchase #5	$82.82	3.373%	$85.6135	$85.61	$85.60	$85.60
Purchase #6	$172.96	10.362%	$190.8821	$190.88	$190.90	$190.90
Purchase #7	$228.64	11.604%	$255.1714	$255.17	$255.15	$255.20
7 purchase totals =	$1,058.13		$1,142.5435	$1,142.53	$1,142.50	$1,142.60