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	$106.69	4.765%	$111.7738	$111.77	$111.75	$111.80
Purchase #2	$228.34	10.174%	$251.5713	$251.57	$251.55	$251.60
Purchase #3	$141.31	6.412%	$150.3708	$150.37	$150.35	$150.40
Purchase #4	$48.65	8.404%	$52.7385	$52.74	$52.75	$52.70
Purchase #5	$95.92	3.527%	$99.3031	$99.30	$99.30	$99.30
Purchase #6	$44.93	6.123%	$47.6811	$47.68	$47.70	$47.70
Purchase #7	$103.47	3.498%	$107.0894	$107.09	$107.10	$107.10
7 purchase totals =	$769.31		$820.5280	$820.52	$820.50	$820.60