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	$206.50	4.269%	$215.3155	$215.32	$215.30	$215.30
Purchase #2	$11.83	10.424%	$13.0632	$13.06	$13.05	$13.10
Purchase #3	$150.51	12.146%	$168.7909	$168.79	$168.80	$168.80
Purchase #4	$73.46	11.765%	$82.1026	$82.10	$82.10	$82.10
Purchase #5	$175.30	4.301%	$182.8397	$182.84	$182.85	$182.80
Purchase #6	$60.35	11.562%	$67.3277	$67.33	$67.35	$67.30
Purchase #7	$161.30	12.404%	$181.3077	$181.31	$181.30	$181.30
7 purchase totals =	$839.25		$910.7473	$910.75	$910.75	$910.70