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	$215.87	4.362%	$225.2862	$225.29	$225.30	$225.30
Purchase #2	$55.38	6.704%	$59.0927	$59.09	$59.10	$59.10
Purchase #3	$67.94	4.499%	$70.9966	$71.00	$71.00	$71.00
Purchase #4	$86.62	6.442%	$92.2001	$92.20	$92.20	$92.20
Purchase #5	$49.72	7.654%	$53.5256	$53.53	$53.55	$53.50
Purchase #6	$102.83	7.465%	$110.5063	$110.51	$110.50	$110.50
Purchase #7	$150.97	10.843%	$167.3397	$167.34	$167.35	$167.30
7 purchase totals =	$729.33		$778.9472	$778.96	$779.00	$778.90