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	$142.97	9.585%	$156.6737	$156.67	$156.65	$156.70
Purchase #2	$211.70	7.711%	$228.0242	$228.02	$228.00	$228.00
Purchase #3	$94.51	4.145%	$98.4274	$98.43	$98.45	$98.40
Purchase #4	$170.89	11.758%	$190.9832	$190.98	$191.00	$191.00
Purchase #5	$224.78	9.210%	$245.4822	$245.48	$245.50	$245.50
Purchase #6	$64.94	11.227%	$72.2308	$72.23	$72.25	$72.20
Purchase #7	$182.81	3.275%	$188.797	$188.80	$188.80	$188.80
7 purchase totals =	$1,092.60		$1,180.6185	$1,180.61	$1,180.65	$1,180.60