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	$191.45	10.132%	$210.8477	$210.85	$210.85	$210.80
Purchase #2	$233.54	5.679%	$246.8027	$246.80	$246.80	$246.80
Purchase #3	$201.30	11.396%	$224.2401	$224.24	$224.25	$224.20
Purchase #4	$152.52	6.487%	$162.414	$162.41	$162.40	$162.40
Purchase #5	$15.46	7.132%	$16.5626	$16.56	$16.55	$16.60
Purchase #6	$51.44	3.607%	$53.2954	$53.30	$53.30	$53.30
Purchase #7	$154.51	11.527%	$172.3204	$172.32	$172.30	$172.30
7 purchase totals =	$1,000.22		$1,086.4829	$1,086.48	$1,086.45	$1,086.40