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	$156.84	6.809%	$167.5192	$167.52	$167.50	$167.50
Purchase #2	$129.71	3.562%	$134.3303	$134.33	$134.35	$134.30
Purchase #3	$59.96	3.158%	$61.8535	$61.85	$61.85	$61.90
Purchase #4	$210.92	8.606%	$229.0718	$229.07	$229.05	$229.10
Purchase #5	$98.43	7.245%	$105.5613	$105.56	$105.55	$105.60
Purchase #6	$187.78	13.677%	$213.4627	$213.46	$213.45	$213.50
Purchase #7	$198.89	3.817%	$206.4816	$206.48	$206.50	$206.50
7 purchase totals =	$1,042.53		$1,118.2804	$1,118.27	$1,118.25	$1,118.40