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	$203.31	7.510%	$218.5786	$218.58	$218.60	$218.60
Purchase #2	$237.65	5.585%	$250.9228	$250.92	$250.90	$250.90
Purchase #3	$207.46	5.841%	$219.5777	$219.58	$219.60	$219.60
Purchase #4	$161.65	12.571%	$181.971	$181.97	$181.95	$182.00
Purchase #5	$82.34	5.501%	$86.8695	$86.87	$86.85	$86.90
Purchase #6	$70.37	3.355%	$72.7309	$72.73	$72.75	$72.70
Purchase #7	$58.42	4.798%	$61.223	$61.22	$61.20	$61.20
7 purchase totals =	$1,021.20		$1,091.8735	$1,091.87	$1,091.85	$1,091.90