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	$167.54	11.522%	$186.844	$186.84	$186.85	$186.80
Purchase #2	$232.61	4.420%	$242.8914	$242.89	$242.90	$242.90
Purchase #3	$168.26	6.756%	$179.6276	$179.63	$179.65	$179.60
Purchase #4	$54.75	4.432%	$57.1765	$57.18	$57.20	$57.20
Purchase #5	$87.33	10.598%	$96.5852	$96.59	$96.60	$96.60
Purchase #6	$90.79	9.199%	$99.1418	$99.14	$99.15	$99.10
Purchase #7	$172.79	11.806%	$193.1896	$193.19	$193.20	$193.20
7 purchase totals =	$974.07		$1,055.4561	$1,055.46	$1,055.55	$1,055.40