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	$219.45	4.362%	$229.0224	$229.02	$229.00	$229.00
Purchase #2	$210.36	8.782%	$228.8338	$228.83	$228.85	$228.80
Purchase #3	$62.89	9.481%	$68.8526	$68.85	$68.85	$68.90
Purchase #4	$93.31	3.858%	$96.9099	$96.91	$96.90	$96.90
Purchase #5	$160.51	7.533%	$172.6012	$172.60	$172.60	$172.60
Purchase #6	$86.33	8.108%	$93.3296	$93.33	$93.35	$93.30
Purchase #7	$103.94	7.313%	$111.5411	$111.54	$111.55	$111.50
7 purchase totals =	$936.79		$1,001.0906	$1,001.08	$1,001.10	$1,001.00