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	$102.36	11.740%	$114.3771	$114.38	$114.40	$114.40
Purchase #2	$7.56	11.137%	$8.402	$8.40	$8.40	$8.40
Purchase #3	$46.54	6.791%	$49.7005	$49.70	$49.70	$49.70
Purchase #4	$64.82	13.202%	$73.3775	$73.38	$73.40	$73.40
Purchase #5	$94.84	11.300%	$105.5569	$105.56	$105.55	$105.60
Purchase #6	$109.34	12.511%	$123.0195	$123.02	$123.00	$123.00
Purchase #7	$90.54	11.562%	$101.0082	$101.01	$101.00	$101.00
7 purchase totals =	$516.00		$575.4417	$575.45	$575.45	$575.50