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	$195.35	13.643%	$222.0016	$222.00	$222.00	$222.00
Purchase #2	$96.72	4.844%	$101.4051	$101.41	$101.40	$101.40
Purchase #3	$33.32	6.867%	$35.6081	$35.61	$35.60	$35.60
Purchase #4	$219.33	10.224%	$241.7543	$241.75	$241.75	$241.80
Purchase #5	$75.85	12.635%	$85.4336	$85.43	$85.45	$85.40
Purchase #6	$109.95	8.151%	$118.912	$118.91	$118.90	$118.90
Purchase #7	$187.89	9.210%	$205.1947	$205.19	$205.20	$205.20
7 purchase totals =	$918.41		$1,010.3094	$1,010.30	$1,010.30	$1,010.30