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	$131.98	11.509%	$147.1696	$147.17	$147.15	$147.20
Purchase #2	$247.58	5.826%	$262.004	$262.00	$262.00	$262.00
Purchase #3	$170.64	5.658%	$180.2948	$180.29	$180.30	$180.30
Purchase #4	$145.53	7.472%	$156.404	$156.40	$156.40	$156.40
Purchase #5	$29.82	10.631%	$32.9902	$32.99	$33.00	$33.00
Purchase #6	$110.50	12.157%	$123.9335	$123.93	$123.95	$123.90
Purchase #7	$99.91	9.817%	$109.7182	$109.72	$109.70	$109.70
7 purchase totals =	$935.96		$1,012.5143	$1,012.50	$1,012.50	$1,012.50