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	$241.48	13.799%	$274.8018	$274.80	$274.80	$274.80
Purchase #2	$228.89	12.334%	$257.1213	$257.12	$257.10	$257.10
Purchase #3	$48.85	5.187%	$51.3838	$51.38	$51.40	$51.40
Purchase #4	$115.46	13.751%	$131.3369	$131.34	$131.35	$131.30
Purchase #5	$79.98	10.593%	$88.4523	$88.45	$88.45	$88.50
Purchase #6	$196.61	13.543%	$223.2369	$223.24	$223.25	$223.20
Purchase #7	$26.69	4.753%	$27.9586	$27.96	$27.95	$28.00
7 purchase totals =	$937.96		$1,054.2916	$1,054.29	$1,054.30	$1,054.30