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	$52.67	10.313%	$58.1019	$58.10	$58.10	$58.10
Purchase #2	$51.45	6.200%	$54.6399	$54.64	$54.65	$54.60
Purchase #3	$42.66	10.414%	$47.1026	$47.10	$47.10	$47.10
Purchase #4	$87.30	3.667%	$90.5013	$90.50	$90.50	$90.50
Purchase #5	$246.74	12.568%	$277.7503	$277.75	$277.75	$277.80
Purchase #6	$73.91	6.177%	$78.4754	$78.48	$78.50	$78.50
Purchase #7	$198.74	8.555%	$215.7422	$215.74	$215.75	$215.70
7 purchase totals =	$753.47		$822.3136	$822.31	$822.35	$822.30