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	$148.85	11.144%	$165.4378	$165.44	$165.45	$165.40
Purchase #2	$92.73	9.458%	$101.5004	$101.50	$101.50	$101.50
Purchase #3	$134.41	13.400%	$152.4209	$152.42	$152.40	$152.40
Purchase #4	$201.52	4.157%	$209.8972	$209.90	$209.90	$209.90
Purchase #5	$58.87	6.753%	$62.8455	$62.85	$62.85	$62.80
Purchase #6	$89.69	6.620%	$95.6275	$95.63	$95.65	$95.60
Purchase #7	$215.52	11.750%	$240.8436	$240.84	$240.85	$240.80
7 purchase totals =	$941.59		$1,028.5729	$1,028.58	$1,028.60	$1,028.40