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	$171.65	6.113%	$182.143	$182.14	$182.15	$182.10
Purchase #2	$106.31	3.842%	$110.3944	$110.39	$110.40	$110.40
Purchase #3	$208.61	4.537%	$218.0746	$218.07	$218.05	$218.10
Purchase #4	$52.50	3.484%	$54.3291	$54.33	$54.35	$54.30
Purchase #5	$182.58	7.690%	$196.6204	$196.62	$196.60	$196.60
Purchase #6	$181.82	8.152%	$196.642	$196.64	$196.65	$196.60
Purchase #7	$149.78	6.857%	$160.0504	$160.05	$160.05	$160.10
7 purchase totals =	$1,053.25		$1,118.2539	$1,118.24	$1,118.25	$1,118.20