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	$212.57	4.573%	$222.2908	$222.29	$222.30	$222.30
Purchase #2	$167.92	10.278%	$185.1788	$185.18	$185.20	$185.20
Purchase #3	$130.85	3.623%	$135.5907	$135.59	$135.60	$135.60
Purchase #4	$178.94	9.532%	$195.9966	$196.00	$196.00	$196.00
Purchase #5	$24.63	13.554%	$27.9684	$27.97	$27.95	$28.00
Purchase #6	$99.94	7.337%	$107.2726	$107.27	$107.25	$107.30
Purchase #7	$221.73	4.452%	$231.6014	$231.60	$231.60	$231.60
7 purchase totals =	$1,036.58		$1,105.8993	$1,105.90	$1,105.90	$1,106.00