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	$75.26	4.161%	$78.3916	$78.39	$78.40	$78.40
Purchase #2	$86.66	5.706%	$91.6048	$91.60	$91.60	$91.60
Purchase #3	$240.56	9.440%	$263.2689	$263.27	$263.25	$263.30
Purchase #4	$246.86	7.231%	$264.7104	$264.71	$264.70	$264.70
Purchase #5	$40.79	5.287%	$42.9466	$42.95	$42.95	$42.90
Purchase #6	$148.54	12.114%	$166.5341	$166.53	$166.55	$166.50
Purchase #7	$104.33	9.814%	$114.5689	$114.57	$114.55	$114.60
7 purchase totals =	$943.00		$1,022.0253	$1,022.02	$1,022.00	$1,022.00