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	$168.72	11.786%	$188.6053	$188.61	$188.60	$188.60
Purchase #2	$152.56	6.204%	$162.0248	$162.02	$162.00	$162.00
Purchase #3	$172.92	12.429%	$194.4122	$194.41	$194.40	$194.40
Purchase #4	$80.96	10.389%	$89.3709	$89.37	$89.35	$89.40
Purchase #5	$156.93	4.229%	$163.5666	$163.57	$163.55	$163.60
Purchase #6	$99.60	6.428%	$106.0023	$106.00	$106.00	$106.00
Purchase #7	$162.91	7.618%	$175.3205	$175.32	$175.30	$175.30
7 purchase totals =	$994.60		$1,079.3026	$1,079.30	$1,079.20	$1,079.30