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	$94.93	11.585%	$105.9276	$105.93	$105.95	$105.90
Purchase #2	$242.87	4.350%	$253.4348	$253.43	$253.45	$253.40
Purchase #3	$65.48	9.215%	$71.514	$71.51	$71.50	$71.50
Purchase #4	$175.51	4.402%	$183.236	$183.24	$183.25	$183.20
Purchase #5	$41.88	9.204%	$45.7346	$45.73	$45.75	$45.70
Purchase #6	$114.73	9.368%	$125.4779	$125.48	$125.50	$125.50
Purchase #7	$82.33	4.783%	$86.2678	$86.27	$86.25	$86.30
7 purchase totals =	$817.73		$871.5927	$871.59	$871.65	$871.50