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	$184.82	3.300%	$190.9191	$190.92	$190.90	$190.90
Purchase #2	$65.72	7.469%	$70.6286	$70.63	$70.65	$70.60
Purchase #3	$83.36	8.127%	$90.1347	$90.13	$90.15	$90.10
Purchase #4	$185.31	11.715%	$207.0191	$207.02	$207.00	$207.00
Purchase #5	$242.88	3.312%	$250.9242	$250.92	$250.90	$250.90
Purchase #6	$97.28	6.868%	$103.9612	$103.96	$103.95	$104.00
Purchase #7	$246.92	10.435%	$272.6861	$272.69	$272.70	$272.70
7 purchase totals =	$1,106.29		$1,186.2730	$1,186.27	$1,186.25	$1,186.20