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	$13.31	7.139%	$14.2602	$14.26	$14.25	$14.30
Purchase #2	$89.37	4.699%	$93.5695	$93.57	$93.55	$93.60
Purchase #3	$81.30	8.866%	$88.5081	$88.51	$88.50	$88.50
Purchase #4	$219.75	10.201%	$242.1667	$242.17	$242.15	$242.20
Purchase #5	$57.27	7.870%	$61.7771	$61.78	$61.80	$61.80
Purchase #6	$249.52	12.809%	$281.481	$281.48	$281.50	$281.50
Purchase #7	$30.28	9.192%	$33.0633	$33.06	$33.05	$33.10
7 purchase totals =	$740.80		$814.8259	$814.83	$814.80	$815.00