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	$83.27	10.477%	$91.9942	$91.99	$92.00	$92.00
Purchase #2	$94.83	5.136%	$99.7005	$99.70	$99.70	$99.70
Purchase #3	$173.57	5.177%	$182.5557	$182.56	$182.55	$182.60
Purchase #4	$226.95	3.386%	$234.6345	$234.63	$234.65	$234.60
Purchase #5	$55.64	6.628%	$59.3278	$59.33	$59.35	$59.30
Purchase #6	$53.58	10.580%	$59.2488	$59.25	$59.25	$59.20
Purchase #7	$128.65	10.406%	$142.0373	$142.04	$142.05	$142.00
7 purchase totals =	$816.49		$869.4988	$869.50	$869.55	$869.40