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	$125.96	4.216%	$131.2705	$131.27	$131.25	$131.30
Purchase #2	$211.50	3.190%	$218.2469	$218.25	$218.25	$218.20
Purchase #3	$179.47	6.665%	$191.4317	$191.43	$191.45	$191.40
Purchase #4	$133.33	8.281%	$144.3711	$144.37	$144.35	$144.40
Purchase #5	$166.75	10.334%	$183.9819	$183.98	$184.00	$184.00
Purchase #6	$128.66	13.526%	$146.0626	$146.06	$146.05	$146.10
Purchase #7	$130.32	4.713%	$136.462	$136.46	$136.45	$136.50
7 purchase totals =	$1,075.99		$1,151.8267	$1,151.82	$1,151.80	$1,151.90