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	$185.67	5.628%	$196.1195	$196.12	$196.10	$196.10
Purchase #2	$130.60	4.418%	$136.3699	$136.37	$136.35	$136.40
Purchase #3	$102.86	5.257%	$108.2674	$108.27	$108.25	$108.30
Purchase #4	$53.96	3.479%	$55.8373	$55.84	$55.85	$55.80
Purchase #5	$95.26	5.260%	$100.2707	$100.27	$100.25	$100.30
Purchase #6	$59.40	7.686%	$63.9655	$63.97	$63.95	$64.00
Purchase #7	$204.92	10.181%	$225.7829	$225.78	$225.80	$225.80
7 purchase totals =	$832.67		$886.6132	$886.62	$886.55	$886.70