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	$177.42	4.733%	$185.8173	$185.82	$185.80	$185.80
Purchase #2	$140.50	6.175%	$149.1759	$149.18	$149.20	$149.20
Purchase #3	$35.53	13.349%	$40.2729	$40.27	$40.25	$40.30
Purchase #4	$144.33	5.599%	$152.411	$152.41	$152.40	$152.40
Purchase #5	$162.95	3.554%	$168.7412	$168.74	$168.75	$168.70
Purchase #6	$127.32	9.672%	$139.6344	$139.63	$139.65	$139.60
Purchase #7	$171.77	11.385%	$191.326	$191.33	$191.35	$191.30
7 purchase totals =	$959.82		$1,027.3787	$1,027.38	$1,027.40	$1,027.30