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	$105.56	3.313%	$109.0572	$109.06	$109.05	$109.10
Purchase #2	$91.58	7.426%	$98.3807	$98.38	$98.40	$98.40
Purchase #3	$129.83	6.675%	$138.4962	$138.50	$138.50	$138.50
Purchase #4	$171.47	4.300%	$178.8432	$178.84	$178.85	$178.80
Purchase #5	$23.67	7.626%	$25.4751	$25.48	$25.50	$25.50
Purchase #6	$121.59	5.237%	$127.9577	$127.96	$127.95	$128.00
Purchase #7	$236.52	11.698%	$264.1881	$264.19	$264.20	$264.20
7 purchase totals =	$880.22		$942.3982	$942.41	$942.45	$942.50