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	$176.45	5.163%	$185.5601	$185.56	$185.55	$185.60
Purchase #2	$99.64	9.139%	$108.7461	$108.75	$108.75	$108.70
Purchase #3	$95.73	5.793%	$101.2756	$101.28	$101.30	$101.30
Purchase #4	$102.34	3.486%	$105.9076	$105.91	$105.90	$105.90
Purchase #5	$68.46	6.444%	$72.8716	$72.87	$72.85	$72.90
Purchase #6	$205.44	7.339%	$220.5172	$220.52	$220.50	$220.50
Purchase #7	$73.32	3.860%	$76.1502	$76.15	$76.15	$76.20
7 purchase totals =	$821.38		$871.0284	$871.04	$871.00	$871.10