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	$240.62	11.480%	$268.2432	$268.24	$268.25	$268.20
Purchase #2	$94.52	4.870%	$99.1231	$99.12	$99.10	$99.10
Purchase #3	$164.59	12.604%	$185.3349	$185.33	$185.35	$185.30
Purchase #4	$54.89	10.257%	$60.5201	$60.52	$60.50	$60.50
Purchase #5	$93.89	12.382%	$105.5155	$105.52	$105.50	$105.50
Purchase #6	$214.74	12.550%	$241.6899	$241.69	$241.70	$241.70
Purchase #7	$122.31	9.391%	$133.7961	$133.80	$133.80	$133.80
7 purchase totals =	$985.56		$1,094.2228	$1,094.22	$1,094.20	$1,094.10