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	$231.69	4.225%	$241.4789	$241.48	$241.50	$241.50
Purchase #2	$238.70	10.654%	$264.1311	$264.13	$264.15	$264.10
Purchase #3	$113.31	4.477%	$118.3829	$118.38	$118.40	$118.40
Purchase #4	$106.72	4.869%	$111.9162	$111.92	$111.90	$111.90
Purchase #5	$75.84	12.615%	$85.4072	$85.41	$85.40	$85.40
Purchase #6	$87.79	11.534%	$97.9157	$97.92	$97.90	$97.90
Purchase #7	$169.78	11.296%	$188.9583	$188.96	$188.95	$189.00
7 purchase totals =	$1,023.83		$1,108.1903	$1,108.20	$1,108.20	$1,108.20