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	$197.47	6.460%	$210.2266	$210.23	$210.25	$210.20
Purchase #2	$35.39	11.341%	$39.4036	$39.40	$39.40	$39.40
Purchase #3	$140.97	4.663%	$147.5434	$147.54	$147.55	$147.50
Purchase #4	$39.68	5.582%	$41.8949	$41.89	$41.90	$41.90
Purchase #5	$160.41	4.634%	$167.8434	$167.84	$167.85	$167.80
Purchase #6	$202.72	11.259%	$225.5442	$225.54	$225.55	$225.50
Purchase #7	$231.66	5.209%	$243.7272	$243.73	$243.75	$243.70
7 purchase totals =	$1,008.30		$1,076.1833	$1,076.17	$1,076.25	$1,076.00