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	$108.90	4.820%	$114.149	$114.15	$114.15	$114.10
Purchase #2	$226.62	11.598%	$252.9034	$252.90	$252.90	$252.90
Purchase #3	$56.44	6.124%	$59.8964	$59.90	$59.90	$59.90
Purchase #4	$62.76	7.842%	$67.6816	$67.68	$67.70	$67.70
Purchase #5	$82.50	11.420%	$91.9215	$91.92	$91.90	$91.90
Purchase #6	$199.87	8.404%	$216.6671	$216.67	$216.65	$216.70
Purchase #7	$206.63	7.775%	$222.6955	$222.70	$222.70	$222.70
7 purchase totals =	$943.72		$1,025.9145	$1,025.92	$1,025.90	$1,025.90