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	$137.92	10.447%	$152.3285	$152.33	$152.35	$152.30
Purchase #2	$168.74	11.753%	$188.572	$188.57	$188.55	$188.60
Purchase #3	$211.82	9.747%	$232.4661	$232.47	$232.45	$232.50
Purchase #4	$244.72	4.683%	$256.1802	$256.18	$256.20	$256.20
Purchase #5	$156.32	11.400%	$174.1405	$174.14	$174.15	$174.10
Purchase #6	$249.36	13.151%	$282.1533	$282.15	$282.15	$282.20
Purchase #7	$14.45	3.330%	$14.9312	$14.93	$14.95	$14.90
7 purchase totals =	$1,183.33		$1,300.7718	$1,300.77	$1,300.80	$1,300.80