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	$75.39	8.588%	$81.8645	$81.86	$81.85	$81.90
Purchase #2	$155.53	4.443%	$162.4402	$162.44	$162.45	$162.40
Purchase #3	$181.36	10.768%	$200.8888	$200.89	$200.90	$200.90
Purchase #4	$223.85	11.456%	$249.4943	$249.49	$249.50	$249.50
Purchase #5	$34.79	8.475%	$37.7385	$37.74	$37.75	$37.70
Purchase #6	$185.64	4.786%	$194.5247	$194.52	$194.50	$194.50
Purchase #7	$55.98	5.539%	$59.0807	$59.08	$59.10	$59.10
7 purchase totals =	$912.54		$986.0317	$986.02	$986.05	$986.00