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	$130.55	13.376%	$148.0124	$148.01	$148.00	$148.00
Purchase #2	$41.66	13.499%	$47.2837	$47.28	$47.30	$47.30
Purchase #3	$17.37	6.855%	$18.5607	$18.56	$18.55	$18.60
Purchase #4	$56.96	12.838%	$64.2725	$64.27	$64.25	$64.30
Purchase #5	$179.86	6.285%	$191.1642	$191.16	$191.15	$191.20
Purchase #6	$56.94	6.514%	$60.6491	$60.65	$60.65	$60.60
Purchase #7	$37.90	5.273%	$39.8985	$39.90	$39.90	$39.90
7 purchase totals =	$521.24		$569.8411	$569.83	$569.80	$569.90