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	$68.78	3.587%	$71.2471	$71.25	$71.25	$71.20
Purchase #2	$94.46	5.650%	$99.797	$99.80	$99.80	$99.80
Purchase #3	$63.59	4.665%	$66.5565	$66.56	$66.55	$66.60
Purchase #4	$171.37	10.342%	$189.0931	$189.09	$189.10	$189.10
Purchase #5	$178.41	3.811%	$185.2092	$185.21	$185.20	$185.20
Purchase #6	$159.33	5.492%	$168.0804	$168.08	$168.10	$168.10
Purchase #7	$246.40	10.417%	$272.0675	$272.07	$272.05	$272.10
7 purchase totals =	$982.34		$1,052.0508	$1,052.06	$1,052.05	$1,052.10