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	$186.96	11.571%	$208.5931	$208.59	$208.60	$208.60
Purchase #2	$232.92	3.243%	$240.4736	$240.47	$240.45	$240.50
Purchase #3	$13.64	7.274%	$14.6322	$14.63	$14.65	$14.60
Purchase #4	$249.94	5.781%	$264.389	$264.39	$264.40	$264.40
Purchase #5	$151.73	13.152%	$171.6855	$171.69	$171.70	$171.70
Purchase #6	$141.42	3.391%	$146.2156	$146.22	$146.20	$146.20
Purchase #7	$49.69	7.332%	$53.3333	$53.33	$53.35	$53.30
7 purchase totals =	$1,026.30		$1,099.3223	$1,099.32	$1,099.35	$1,099.30