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	$93.50	6.301%	$99.3914	$99.39	$99.40	$99.40
Purchase #2	$41.43	5.566%	$43.736	$43.74	$43.75	$43.70
Purchase #3	$150.33	4.658%	$157.3324	$157.33	$157.35	$157.30
Purchase #4	$164.43	3.851%	$170.7622	$170.76	$170.75	$170.80
Purchase #5	$93.87	12.298%	$105.4141	$105.41	$105.40	$105.40
Purchase #6	$234.58	13.663%	$266.6307	$266.63	$266.65	$266.60
Purchase #7	$224.50	6.346%	$238.7468	$238.75	$238.75	$238.70
7 purchase totals =	$1,002.64		$1,082.0136	$1,082.01	$1,082.05	$1,081.90