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	$213.43	4.150%	$222.2873	$222.29	$222.30	$222.30
Purchase #2	$101.97	9.519%	$111.6765	$111.68	$111.70	$111.70
Purchase #3	$237.48	5.720%	$251.0639	$251.06	$251.05	$251.10
Purchase #4	$144.79	13.463%	$164.2831	$164.28	$164.30	$164.30
Purchase #5	$29.69	6.292%	$31.5581	$31.56	$31.55	$31.60
Purchase #6	$198.45	7.607%	$213.5461	$213.55	$213.55	$213.50
Purchase #7	$12.91	7.191%	$13.8384	$13.84	$13.85	$13.80
7 purchase totals =	$938.72		$1,008.2534	$1,008.26	$1,008.30	$1,008.30