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	$145.51	4.561%	$152.1467	$152.15	$152.15	$152.10
Purchase #2	$65.63	4.351%	$68.4856	$68.49	$68.50	$68.50
Purchase #3	$84.57	6.257%	$89.8615	$89.86	$89.85	$89.90
Purchase #4	$218.29	11.586%	$243.5811	$243.58	$243.60	$243.60
Purchase #5	$157.86	10.263%	$174.0612	$174.06	$174.05	$174.10
Purchase #6	$79.44	4.734%	$83.2007	$83.20	$83.20	$83.20
Purchase #7	$78.30	10.578%	$86.5826	$86.58	$86.60	$86.60
7 purchase totals =	$829.60		$897.9194	$897.92	$897.95	$898.00