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	$181.35	8.187%	$196.1971	$196.20	$196.20	$196.20
Purchase #2	$162.80	11.425%	$181.3999	$181.40	$181.40	$181.40
Purchase #3	$79.82	13.495%	$90.5917	$90.59	$90.60	$90.60
Purchase #4	$164.35	12.412%	$184.7491	$184.75	$184.75	$184.70
Purchase #5	$236.31	13.718%	$268.727	$268.73	$268.75	$268.70
Purchase #6	$165.93	11.231%	$184.5656	$184.57	$184.55	$184.60
Purchase #7	$166.92	8.638%	$181.3385	$181.34	$181.35	$181.30
7 purchase totals =	$1,157.48		$1,287.5689	$1,287.58	$1,287.60	$1,287.50