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	$65.40	10.773%	$72.4455	$72.45	$72.45	$72.40
Purchase #2	$88.31	3.734%	$91.6075	$91.61	$91.60	$91.60
Purchase #3	$208.47	8.461%	$226.1086	$226.11	$226.10	$226.10
Purchase #4	$64.99	4.303%	$67.7865	$67.79	$67.80	$67.80
Purchase #5	$96.33	8.773%	$104.781	$104.78	$104.80	$104.80
Purchase #6	$128.28	4.365%	$133.8794	$133.88	$133.90	$133.90
Purchase #7	$166.90	13.146%	$188.8407	$188.84	$188.85	$188.80
7 purchase totals =	$818.68		$885.4492	$885.46	$885.50	$885.40