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	$70.26	5.400%	$74.054	$74.05	$74.05	$74.10
Purchase #2	$50.60	4.813%	$53.0354	$53.04	$53.05	$53.00
Purchase #3	$80.85	11.752%	$90.3515	$90.35	$90.35	$90.40
Purchase #4	$175.92	4.804%	$184.3712	$184.37	$184.35	$184.40
Purchase #5	$126.25	6.822%	$134.8628	$134.86	$134.85	$134.90
Purchase #6	$81.25	11.429%	$90.5361	$90.54	$90.55	$90.50
Purchase #7	$127.42	11.671%	$142.2912	$142.29	$142.30	$142.30
7 purchase totals =	$712.55		$769.5022	$769.50	$769.50	$769.60