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	$219.85	3.392%	$227.3073	$227.31	$227.30	$227.30
Purchase #2	$63.40	4.407%	$66.194	$66.19	$66.20	$66.20
Purchase #3	$93.58	6.765%	$99.9107	$99.91	$99.90	$99.90
Purchase #4	$37.33	9.819%	$40.9954	$41.00	$41.00	$41.00
Purchase #5	$83.92	7.135%	$89.9077	$89.91	$89.90	$89.90
Purchase #6	$171.42	9.248%	$187.2729	$187.27	$187.25	$187.30
Purchase #7	$186.63	10.699%	$206.5975	$206.60	$206.60	$206.60
7 purchase totals =	$856.13		$918.1855	$918.19	$918.15	$918.20