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	$54.40	9.269%	$59.4423	$59.44	$59.45	$59.40
Purchase #2	$27.48	6.528%	$29.2739	$29.27	$29.25	$29.30
Purchase #3	$79.61	12.462%	$89.531	$89.53	$89.55	$89.50
Purchase #4	$245.94	9.170%	$268.4927	$268.49	$268.50	$268.50
Purchase #5	$240.41	4.444%	$251.0938	$251.09	$251.10	$251.10
Purchase #6	$155.89	11.659%	$174.0652	$174.07	$174.05	$174.10
Purchase #7	$62.34	11.838%	$69.7198	$69.72	$69.70	$69.70
7 purchase totals =	$866.07		$941.6187	$941.61	$941.60	$941.60