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	$164.82	7.693%	$177.4996	$177.50	$177.50	$177.50
Purchase #2	$54.80	4.415%	$57.2194	$57.22	$57.20	$57.20
Purchase #3	$219.66	12.138%	$246.3223	$246.32	$246.30	$246.30
Purchase #4	$165.95	9.192%	$181.2041	$181.20	$181.20	$181.20
Purchase #5	$113.59	4.121%	$118.271	$118.27	$118.25	$118.30
Purchase #6	$158.37	4.396%	$165.3319	$165.33	$165.35	$165.30
Purchase #7	$184.35	6.658%	$196.624	$196.62	$196.60	$196.60
7 purchase totals =	$1,061.54		$1,142.4723	$1,142.46	$1,142.40	$1,142.40