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	$167.46	9.578%	$183.4993	$183.50	$183.50	$183.50
Purchase #2	$179.92	9.378%	$196.7929	$196.79	$196.80	$196.80
Purchase #3	$146.69	10.484%	$162.069	$162.07	$162.05	$162.10
Purchase #4	$31.27	6.528%	$33.3113	$33.31	$33.30	$33.30
Purchase #5	$96.65	9.329%	$105.6665	$105.67	$105.65	$105.70
Purchase #6	$174.83	4.851%	$183.311	$183.31	$183.30	$183.30
Purchase #7	$238.50	4.543%	$249.3351	$249.34	$249.35	$249.30
7 purchase totals =	$1,035.32		$1,113.9851	$1,113.99	$1,113.95	$1,114.00