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	$97.30	11.311%	$108.3056	$108.31	$108.30	$108.30
Purchase #2	$180.64	4.417%	$188.6189	$188.62	$188.60	$188.60
Purchase #3	$194.59	12.530%	$218.9721	$218.97	$218.95	$219.00
Purchase #4	$196.85	5.800%	$208.2673	$208.27	$208.25	$208.30
Purchase #5	$166.66	5.813%	$176.3479	$176.35	$176.35	$176.30
Purchase #6	$53.64	11.186%	$59.6402	$59.64	$59.65	$59.60
Purchase #7	$224.58	11.432%	$250.254	$250.25	$250.25	$250.30
7 purchase totals =	$1,114.26		$1,210.4060	$1,210.41	$1,210.35	$1,210.40