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	$79.34	9.124%	$86.579	$86.58	$86.60	$86.60
Purchase #2	$249.95	4.851%	$262.0751	$262.08	$262.10	$262.10
Purchase #3	$151.69	13.118%	$171.5887	$171.59	$171.60	$171.60
Purchase #4	$135.46	10.137%	$149.1916	$149.19	$149.20	$149.20
Purchase #5	$134.89	12.393%	$151.6069	$151.61	$151.60	$151.60
Purchase #6	$32.86	3.295%	$33.9427	$33.94	$33.95	$33.90
Purchase #7	$176.91	13.220%	$200.2975	$200.30	$200.30	$200.30
7 purchase totals =	$961.10		$1,055.2815	$1,055.29	$1,055.35	$1,055.30