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	$53.74	10.819%	$59.5541	$59.55	$59.55	$59.60
Purchase #2	$203.85	5.519%	$215.1005	$215.10	$215.10	$215.10
Purchase #3	$20.64	10.518%	$22.8109	$22.81	$22.80	$22.80
Purchase #4	$148.47	7.610%	$159.7686	$159.77	$159.75	$159.80
Purchase #5	$47.83	9.845%	$52.5389	$52.54	$52.55	$52.50
Purchase #6	$181.55	3.297%	$187.5357	$187.54	$187.55	$187.50
Purchase #7	$10.90	13.147%	$12.333	$12.33	$12.35	$12.30
7 purchase totals =	$666.98		$709.6417	$709.64	$709.65	$709.60