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	$161.71	11.589%	$180.4506	$180.45	$180.45	$180.50
Purchase #2	$131.94	11.712%	$147.3928	$147.39	$147.40	$147.40
Purchase #3	$74.54	6.489%	$79.3769	$79.38	$79.40	$79.40
Purchase #4	$23.70	7.798%	$25.5481	$25.55	$25.55	$25.50
Purchase #5	$41.26	9.870%	$45.3324	$45.33	$45.35	$45.30
Purchase #6	$47.44	13.629%	$53.9056	$53.91	$53.90	$53.90
Purchase #7	$169.72	12.395%	$190.7568	$190.76	$190.75	$190.80
7 purchase totals =	$650.31		$722.7632	$722.77	$722.80	$722.80