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	$240.41	7.335%	$258.0441	$258.04	$258.05	$258.00
Purchase #2	$29.94	11.325%	$33.3307	$33.33	$33.35	$33.30
Purchase #3	$46.61	9.703%	$51.1326	$51.13	$51.15	$51.10
Purchase #4	$56.63	5.780%	$59.9032	$59.90	$59.90	$59.90
Purchase #5	$99.68	4.196%	$103.8626	$103.86	$103.85	$103.90
Purchase #6	$124.68	7.568%	$134.1158	$134.12	$134.10	$134.10
Purchase #7	$59.87	3.685%	$62.0762	$62.08	$62.10	$62.10
7 purchase totals =	$657.82		$702.4652	$702.46	$702.50	$702.40