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	$160.97	9.279%	$175.9064	$175.91	$175.90	$175.90
Purchase #2	$180.37	6.744%	$192.5342	$192.53	$192.55	$192.50
Purchase #3	$59.80	4.528%	$62.5077	$62.51	$62.50	$62.50
Purchase #4	$127.80	9.860%	$140.4011	$140.40	$140.40	$140.40
Purchase #5	$73.60	11.827%	$82.3047	$82.30	$82.30	$82.30
Purchase #6	$152.38	4.412%	$159.103	$159.10	$159.10	$159.10
Purchase #7	$229.98	10.853%	$254.9397	$254.94	$254.95	$254.90
7 purchase totals =	$984.90		$1,067.6968	$1,067.69	$1,067.70	$1,067.60