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	$118.39	13.623%	$134.5183	$134.52	$134.50	$134.50
Purchase #2	$32.46	10.152%	$35.7553	$35.76	$35.75	$35.80
Purchase #3	$132.60	5.251%	$139.5628	$139.56	$139.55	$139.60
Purchase #4	$139.60	5.305%	$147.0058	$147.01	$147.00	$147.00
Purchase #5	$112.43	9.816%	$123.4661	$123.47	$123.45	$123.50
Purchase #6	$237.85	11.200%	$264.4892	$264.49	$264.50	$264.50
Purchase #7	$165.32	8.615%	$179.5623	$179.56	$179.55	$179.60
7 purchase totals =	$938.65		$1,024.3598	$1,024.37	$1,024.30	$1,024.50