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	$211.58	13.849%	$240.8817	$240.88	$240.90	$240.90
Purchase #2	$17.56	5.623%	$18.5474	$18.55	$18.55	$18.50
Purchase #3	$143.46	8.390%	$155.4963	$155.50	$155.50	$155.50
Purchase #4	$164.42	11.372%	$183.1178	$183.12	$183.10	$183.10
Purchase #5	$98.55	12.790%	$111.1545	$111.15	$111.15	$111.20
Purchase #6	$187.37	11.562%	$209.0337	$209.03	$209.05	$209.00
Purchase #7	$81.50	5.489%	$85.9735	$85.97	$85.95	$86.00
7 purchase totals =	$904.44		$1,004.2049	$1,004.20	$1,004.20	$1,004.20