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	$156.94	7.608%	$168.88	$168.88	$168.90	$168.90
Purchase #2	$248.79	5.367%	$262.1426	$262.14	$262.15	$262.10
Purchase #3	$94.31	6.122%	$100.0837	$100.08	$100.10	$100.10
Purchase #4	$240.73	10.720%	$266.5363	$266.54	$266.55	$266.50
Purchase #5	$42.59	4.244%	$44.3975	$44.40	$44.40	$44.40
Purchase #6	$229.48	10.407%	$253.362	$253.36	$253.35	$253.40
Purchase #7	$157.70	10.284%	$173.9179	$173.92	$173.90	$173.90
7 purchase totals =	$1,170.54		$1,269.3200	$1,269.32	$1,269.35	$1,269.30