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	$119.96	11.515%	$133.7734	$133.77	$133.75	$133.80
Purchase #2	$211.96	10.446%	$234.1013	$234.10	$234.10	$234.10
Purchase #3	$156.28	5.862%	$165.4411	$165.44	$165.45	$165.40
Purchase #4	$110.90	8.808%	$120.6681	$120.67	$120.65	$120.70
Purchase #5	$70.47	11.243%	$78.3929	$78.39	$78.40	$78.40
Purchase #6	$163.59	9.106%	$178.4865	$178.49	$178.50	$178.50
Purchase #7	$40.69	5.483%	$42.921	$42.92	$42.90	$42.90
7 purchase totals =	$873.85		$953.7843	$953.78	$953.75	$953.80