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	$131.82	3.134%	$135.9512	$135.95	$135.95	$136.00
Purchase #2	$100.40	9.405%	$109.8426	$109.84	$109.85	$109.80
Purchase #3	$154.75	6.793%	$165.2622	$165.26	$165.25	$165.30
Purchase #4	$81.55	12.242%	$91.5334	$91.53	$91.55	$91.50
Purchase #5	$248.91	5.851%	$263.4737	$263.47	$263.45	$263.50
Purchase #6	$123.64	3.589%	$128.0774	$128.08	$128.10	$128.10
Purchase #7	$117.47	11.310%	$130.7559	$130.76	$130.75	$130.80
7 purchase totals =	$958.54		$1,024.8964	$1,024.89	$1,024.90	$1,025.00