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	$92.96	5.168%	$97.7642	$97.76	$97.75	$97.80
Purchase #2	$119.85	4.726%	$125.5141	$125.51	$125.50	$125.50
Purchase #3	$39.61	4.293%	$41.3105	$41.31	$41.30	$41.30
Purchase #4	$240.34	9.534%	$263.254	$263.25	$263.25	$263.30
Purchase #5	$104.68	6.322%	$111.2979	$111.30	$111.30	$111.30
Purchase #6	$62.73	7.641%	$67.5232	$67.52	$67.50	$67.50
Purchase #7	$115.86	12.511%	$130.3552	$130.36	$130.35	$130.40
7 purchase totals =	$776.03		$837.0191	$837.01	$836.95	$837.10