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	$222.53	6.322%	$236.5983	$236.60	$236.60	$236.60
Purchase #2	$157.61	13.793%	$179.3491	$179.35	$179.35	$179.30
Purchase #3	$89.84	11.376%	$100.0602	$100.06	$100.05	$100.10
Purchase #4	$19.55	6.103%	$20.7431	$20.74	$20.75	$20.70
Purchase #5	$243.50	9.358%	$266.2867	$266.29	$266.30	$266.30
Purchase #6	$72.73	13.509%	$82.5551	$82.56	$82.55	$82.60
Purchase #7	$77.43	3.160%	$79.8768	$79.88	$79.90	$79.90
7 purchase totals =	$883.19		$965.4693	$965.48	$965.50	$965.50