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	$200.32	5.294%	$210.9249	$210.92	$210.90	$210.90
Purchase #2	$133.46	4.513%	$139.483	$139.48	$139.50	$139.50
Purchase #3	$167.78	12.116%	$188.1082	$188.11	$188.10	$188.10
Purchase #4	$93.64	4.163%	$97.5382	$97.54	$97.55	$97.50
Purchase #5	$113.79	13.693%	$129.3713	$129.37	$129.35	$129.40
Purchase #6	$196.32	6.671%	$209.4165	$209.42	$209.40	$209.40
Purchase #7	$180.40	8.868%	$196.3979	$196.40	$196.40	$196.40
7 purchase totals =	$1,085.71		$1,171.2400	$1,171.24	$1,171.20	$1,171.20