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	$167.94	10.303%	$185.2429	$185.24	$185.25	$185.20
Purchase #2	$176.91	11.360%	$197.007	$197.01	$197.00	$197.00
Purchase #3	$160.78	11.260%	$178.8838	$178.88	$178.90	$178.90
Purchase #4	$199.77	6.828%	$213.4103	$213.41	$213.40	$213.40
Purchase #5	$211.61	8.865%	$230.3692	$230.37	$230.35	$230.40
Purchase #6	$89.52	11.576%	$99.8828	$99.88	$99.90	$99.90
Purchase #7	$128.31	12.113%	$143.8522	$143.85	$143.85	$143.90
7 purchase totals =	$1,134.84		$1,248.6482	$1,248.64	$1,248.65	$1,248.70