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	$196.66	6.762%	$209.9581	$209.96	$209.95	$210.00
Purchase #2	$19.87	7.551%	$21.3704	$21.37	$21.35	$21.40
Purchase #3	$82.95	8.374%	$89.8962	$89.90	$89.90	$89.90
Purchase #4	$60.97	11.690%	$68.0974	$68.10	$68.10	$68.10
Purchase #5	$25.88	8.723%	$28.1375	$28.14	$28.15	$28.10
Purchase #6	$173.83	4.365%	$181.4177	$181.42	$181.40	$181.40
Purchase #7	$164.33	12.310%	$184.559	$184.56	$184.55	$184.60
7 purchase totals =	$724.49		$783.4363	$783.45	$783.40	$783.50