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	$216.34	12.725%	$243.8693	$243.87	$243.85	$243.90
Purchase #2	$58.88	5.255%	$61.9741	$61.97	$61.95	$62.00
Purchase #3	$162.76	12.495%	$183.0969	$183.10	$183.10	$183.10
Purchase #4	$75.26	13.282%	$85.256	$85.26	$85.25	$85.30
Purchase #5	$217.59	4.817%	$228.0713	$228.07	$228.05	$228.10
Purchase #6	$115.97	6.435%	$123.4327	$123.43	$123.45	$123.40
Purchase #7	$84.26	7.118%	$90.2576	$90.26	$90.25	$90.30
7 purchase totals =	$931.06		$1,015.9579	$1,015.96	$1,015.90	$1,016.10