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	$160.75	7.470%	$172.758	$172.76	$172.75	$172.80
Purchase #2	$26.38	7.221%	$28.2849	$28.28	$28.30	$28.30
Purchase #3	$9.31	10.312%	$10.27	$10.27	$10.25	$10.30
Purchase #4	$89.49	5.141%	$94.0907	$94.09	$94.10	$94.10
Purchase #5	$162.76	13.598%	$184.8921	$184.89	$184.90	$184.90
Purchase #6	$78.98	13.723%	$89.8184	$89.82	$89.80	$89.80
Purchase #7	$70.93	12.285%	$79.6438	$79.64	$79.65	$79.60
7 purchase totals =	$598.60		$659.7579	$659.75	$659.75	$659.80