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	$181.54	5.742%	$191.964	$191.96	$191.95	$192.00
Purchase #2	$219.94	9.832%	$241.5645	$241.56	$241.55	$241.60
Purchase #3	$157.84	6.690%	$168.3995	$168.40	$168.40	$168.40
Purchase #4	$148.91	10.395%	$164.3892	$164.39	$164.40	$164.40
Purchase #5	$211.44	6.629%	$225.4564	$225.46	$225.45	$225.50
Purchase #6	$7.69	3.707%	$7.9751	$7.98	$8.00	$8.00
Purchase #7	$111.41	11.411%	$124.123	$124.12	$124.10	$124.10
7 purchase totals =	$1,038.77		$1,123.8717	$1,123.87	$1,123.85	$1,124.00