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	$145.88	11.437%	$162.5643	$162.56	$162.55	$162.60
Purchase #2	$240.51	12.349%	$270.2106	$270.21	$270.20	$270.20
Purchase #3	$77.74	7.427%	$83.5137	$83.51	$83.50	$83.50
Purchase #4	$178.75	5.165%	$187.9824	$187.98	$188.00	$188.00
Purchase #5	$150.73	6.415%	$160.3993	$160.40	$160.40	$160.40
Purchase #6	$41.87	6.217%	$44.4731	$44.47	$44.45	$44.50
Purchase #7	$156.86	3.792%	$162.8081	$162.81	$162.80	$162.80
7 purchase totals =	$992.34		$1,071.9515	$1,071.94	$1,071.90	$1,072.00