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	$162.37	10.473%	$179.375	$179.38	$179.40	$179.40
Purchase #2	$172.77	11.647%	$192.8925	$192.89	$192.90	$192.90
Purchase #3	$6.36	6.518%	$6.7745	$6.77	$6.75	$6.80
Purchase #4	$94.94	4.251%	$98.9759	$98.98	$99.00	$99.00
Purchase #5	$50.82	12.789%	$57.3194	$57.32	$57.30	$57.30
Purchase #6	$199.80	11.312%	$222.4014	$222.40	$222.40	$222.40
Purchase #7	$230.79	9.265%	$252.1727	$252.17	$252.15	$252.20
7 purchase totals =	$917.85		$1,009.9114	$1,009.91	$1,009.90	$1,010.00