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	$115.81	5.403%	$122.0672	$122.07	$122.05	$122.10
Purchase #2	$196.77	4.637%	$205.8942	$205.89	$205.90	$205.90
Purchase #3	$91.52	3.670%	$94.8788	$94.88	$94.90	$94.90
Purchase #4	$196.30	10.204%	$216.3305	$216.33	$216.35	$216.30
Purchase #5	$111.92	13.817%	$127.384	$127.38	$127.40	$127.40
Purchase #6	$162.69	8.109%	$175.8825	$175.88	$175.90	$175.90
Purchase #7	$81.63	5.569%	$86.176	$86.18	$86.20	$86.20
7 purchase totals =	$956.64		$1,028.6132	$1,028.61	$1,028.70	$1,028.70