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	$128.33	11.207%	$142.7119	$142.71	$142.70	$142.70
Purchase #2	$227.44	7.659%	$244.8596	$244.86	$244.85	$244.90
Purchase #3	$234.55	6.805%	$250.5111	$250.51	$250.50	$250.50
Purchase #4	$140.41	11.608%	$156.7088	$156.71	$156.70	$156.70
Purchase #5	$113.38	12.396%	$127.4346	$127.43	$127.45	$127.40
Purchase #6	$140.51	7.129%	$150.527	$150.53	$150.55	$150.50
Purchase #7	$75.69	12.271%	$84.9779	$84.98	$85.00	$85.00
7 purchase totals =	$1,060.31		$1,157.7309	$1,157.73	$1,157.75	$1,157.70