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	$179.42	3.244%	$185.2404	$185.24	$185.25	$185.20
Purchase #2	$211.38	3.569%	$218.9242	$218.92	$218.90	$218.90
Purchase #3	$121.32	9.132%	$132.3989	$132.40	$132.40	$132.40
Purchase #4	$163.92	4.656%	$171.5521	$171.55	$171.55	$171.60
Purchase #5	$64.34	11.211%	$71.5532	$71.55	$71.55	$71.60
Purchase #6	$50.91	10.437%	$56.2235	$56.22	$56.20	$56.20
Purchase #7	$210.57	5.599%	$222.3598	$222.36	$222.35	$222.40
7 purchase totals =	$1,001.86		$1,058.2521	$1,058.24	$1,058.20	$1,058.30