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	$208.67	9.803%	$229.1259	$229.13	$229.15	$229.10
Purchase #2	$191.83	4.244%	$199.9713	$199.97	$199.95	$200.00
Purchase #3	$113.34	10.189%	$124.8882	$124.89	$124.90	$124.90
Purchase #4	$190.41	4.113%	$198.2416	$198.24	$198.25	$198.20
Purchase #5	$106.42	4.510%	$111.2195	$111.22	$111.20	$111.20
Purchase #6	$220.34	6.374%	$234.3845	$234.38	$234.40	$234.40
Purchase #7	$83.61	6.781%	$89.2796	$89.28	$89.30	$89.30
7 purchase totals =	$1,114.62		$1,187.1106	$1,187.11	$1,187.15	$1,187.10