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	$64.43	12.732%	$72.6332	$72.63	$72.65	$72.60
Purchase #2	$90.92	6.597%	$96.918	$96.92	$96.90	$96.90
Purchase #3	$196.88	11.653%	$219.8224	$219.82	$219.80	$219.80
Purchase #4	$30.45	9.315%	$33.2864	$33.29	$33.30	$33.30
Purchase #5	$106.44	6.386%	$113.2373	$113.24	$113.25	$113.20
Purchase #6	$221.86	12.376%	$249.3174	$249.32	$249.30	$249.30
Purchase #7	$74.44	5.200%	$78.3109	$78.31	$78.30	$78.30
7 purchase totals =	$785.42		$863.5256	$863.53	$863.50	$863.40