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	$142.32	7.514%	$153.0139	$153.01	$153.00	$153.00
Purchase #2	$53.36	10.378%	$58.8977	$58.90	$58.90	$58.90
Purchase #3	$109.61	6.611%	$116.8563	$116.86	$116.85	$116.90
Purchase #4	$85.42	4.211%	$89.017	$89.02	$89.00	$89.00
Purchase #5	$170.25	10.469%	$188.0735	$188.07	$188.05	$188.10
Purchase #6	$234.30	6.132%	$248.6673	$248.67	$248.65	$248.70
Purchase #7	$146.28	8.847%	$159.2214	$159.22	$159.20	$159.20
7 purchase totals =	$941.54		$1,013.7471	$1,013.75	$1,013.65	$1,013.80