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	$162.36	11.242%	$180.6125	$180.61	$180.60	$180.60
Purchase #2	$180.37	3.602%	$186.8669	$186.87	$186.85	$186.90
Purchase #3	$35.83	4.221%	$37.3424	$37.34	$37.35	$37.30
Purchase #4	$228.37	9.641%	$250.3872	$250.39	$250.40	$250.40
Purchase #5	$240.63	4.293%	$250.9602	$250.96	$250.95	$251.00
Purchase #6	$206.31	6.279%	$219.2642	$219.26	$219.25	$219.30
Purchase #7	$169.44	5.720%	$179.132	$179.13	$179.15	$179.10
7 purchase totals =	$1,223.31		$1,304.5654	$1,304.56	$1,304.55	$1,304.60