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	$71.31	10.185%	$78.5729	$78.57	$78.55	$78.60
Purchase #2	$69.26	10.870%	$76.7886	$76.79	$76.80	$76.80
Purchase #3	$41.73	10.168%	$45.9731	$45.97	$45.95	$46.00
Purchase #4	$59.34	7.298%	$63.6706	$63.67	$63.65	$63.70
Purchase #5	$250.85	5.790%	$265.3742	$265.37	$265.35	$265.40
Purchase #6	$114.86	12.236%	$128.9143	$128.91	$128.90	$128.90
Purchase #7	$60.28	4.600%	$63.0529	$63.05	$63.05	$63.10
7 purchase totals =	$667.63		$722.3466	$722.33	$722.25	$722.50