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	$173.92	10.818%	$192.7347	$192.73	$192.75	$192.70
Purchase #2	$57.93	13.844%	$65.9498	$65.95	$65.95	$65.90
Purchase #3	$67.25	5.460%	$70.9219	$70.92	$70.90	$70.90
Purchase #4	$242.83	8.466%	$263.388	$263.39	$263.40	$263.40
Purchase #5	$28.98	12.467%	$32.5929	$32.59	$32.60	$32.60
Purchase #6	$85.56	8.572%	$92.8942	$92.89	$92.90	$92.90
Purchase #7	$212.77	10.601%	$235.3257	$235.33	$235.35	$235.30
7 purchase totals =	$869.24		$953.8072	$953.80	$953.85	$953.70