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	$232.77	12.776%	$262.5087	$262.51	$262.50	$262.50
Purchase #2	$132.42	11.265%	$147.3371	$147.34	$147.35	$147.30
Purchase #3	$92.74	13.519%	$105.2775	$105.28	$105.30	$105.30
Purchase #4	$71.26	12.653%	$80.2765	$80.28	$80.30	$80.30
Purchase #5	$167.89	6.346%	$178.5443	$178.54	$178.55	$178.50
Purchase #6	$165.33	9.486%	$181.0132	$181.01	$181.00	$181.00
Purchase #7	$205.58	3.835%	$213.464	$213.46	$213.45	$213.50
7 purchase totals =	$1,067.99		$1,168.4213	$1,168.42	$1,168.45	$1,168.40