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	$156.27	10.286%	$172.3439	$172.34	$172.35	$172.30
Purchase #2	$91.77	9.350%	$100.3505	$100.35	$100.35	$100.40
Purchase #3	$89.41	10.715%	$98.9903	$98.99	$99.00	$99.00
Purchase #4	$201.92	10.840%	$223.8081	$223.81	$223.80	$223.80
Purchase #5	$181.46	10.524%	$200.5569	$200.56	$200.55	$200.60
Purchase #6	$157.37	4.352%	$164.2187	$164.22	$164.20	$164.20
Purchase #7	$216.68	5.270%	$228.099	$228.10	$228.10	$228.10
7 purchase totals =	$1,094.88		$1,188.3674	$1,188.37	$1,188.35	$1,188.40