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	$155.91	5.296%	$164.167	$164.17	$164.15	$164.20
Purchase #2	$224.43	9.195%	$245.0663	$245.07	$245.05	$245.10
Purchase #3	$199.92	11.180%	$222.2711	$222.27	$222.25	$222.30
Purchase #4	$128.26	11.208%	$142.6354	$142.64	$142.65	$142.60
Purchase #5	$43.30	9.269%	$47.3135	$47.31	$47.30	$47.30
Purchase #6	$167.69	5.248%	$176.4904	$176.49	$176.50	$176.50
Purchase #7	$148.88	9.346%	$162.7943	$162.79	$162.80	$162.80
7 purchase totals =	$1,068.39		$1,160.7380	$1,160.74	$1,160.70	$1,160.80