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	$45.62	3.857%	$47.3796	$47.38	$47.40	$47.40
Purchase #2	$71.34	9.763%	$78.3049	$78.30	$78.30	$78.30
Purchase #3	$91.35	4.706%	$95.6489	$95.65	$95.65	$95.60
Purchase #4	$164.82	5.274%	$173.5126	$173.51	$173.50	$173.50
Purchase #5	$32.48	5.384%	$34.2287	$34.23	$34.25	$34.20
Purchase #6	$88.37	9.665%	$96.911	$96.91	$96.90	$96.90
Purchase #7	$234.55	13.544%	$266.3175	$266.32	$266.30	$266.30
7 purchase totals =	$728.53		$792.3032	$792.30	$792.30	$792.20