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	$69.90	7.789%	$75.3445	$75.34	$75.35	$75.30
Purchase #2	$5.28	4.676%	$5.5269	$5.53	$5.55	$5.50
Purchase #3	$12.44	7.452%	$13.367	$13.37	$13.35	$13.40
Purchase #4	$55.44	10.574%	$61.3022	$61.30	$61.30	$61.30
Purchase #5	$75.37	6.744%	$80.453	$80.45	$80.45	$80.50
Purchase #6	$55.36	11.143%	$61.5288	$61.53	$61.55	$61.50
Purchase #7	$81.37	10.606%	$90.0001	$90.00	$90.00	$90.00
7 purchase totals =	$355.16		$387.5225	$387.52	$387.55	$387.50