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	$201.64	4.508%	$210.7299	$210.73	$210.75	$210.70
Purchase #2	$72.33	13.314%	$81.96	$81.96	$81.95	$82.00
Purchase #3	$105.93	4.599%	$110.8017	$110.80	$110.80	$110.80
Purchase #4	$182.69	3.843%	$189.7108	$189.71	$189.70	$189.70
Purchase #5	$136.95	10.870%	$151.8365	$151.84	$151.85	$151.80
Purchase #6	$127.33	13.573%	$144.6125	$144.61	$144.60	$144.60
Purchase #7	$126.79	3.566%	$131.3113	$131.31	$131.30	$131.30
7 purchase totals =	$953.66		$1,020.9627	$1,020.96	$1,020.95	$1,020.90