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	$129.78	11.560%	$144.7826	$144.78	$144.80	$144.80
Purchase #2	$60.92	11.218%	$67.754	$67.75	$67.75	$67.80
Purchase #3	$196.42	11.797%	$219.5917	$219.59	$219.60	$219.60
Purchase #4	$88.25	11.612%	$98.4976	$98.50	$98.50	$98.50
Purchase #5	$173.68	3.423%	$179.6251	$179.63	$179.65	$179.60
Purchase #6	$247.77	4.285%	$258.3869	$258.39	$258.40	$258.40
Purchase #7	$99.59	12.514%	$112.0527	$112.05	$112.05	$112.10
7 purchase totals =	$996.41		$1,080.6906	$1,080.69	$1,080.75	$1,080.80