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	$229.64	4.408%	$239.7625	$239.76	$239.75	$239.80
Purchase #2	$108.63	7.152%	$116.3992	$116.40	$116.40	$116.40
Purchase #3	$94.60	12.370%	$106.302	$106.30	$106.30	$106.30
Purchase #4	$243.89	4.844%	$255.704	$255.70	$255.70	$255.70
Purchase #5	$160.32	6.696%	$171.055	$171.06	$171.05	$171.10
Purchase #6	$92.26	7.827%	$99.4812	$99.48	$99.50	$99.50
Purchase #7	$155.39	5.590%	$164.0763	$164.08	$164.10	$164.10
7 purchase totals =	$1,084.73		$1,152.7802	$1,152.78	$1,152.80	$1,152.90