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	$36.83	10.642%	$40.7494	$40.75	$40.75	$40.70
Purchase #2	$123.90	11.828%	$138.5549	$138.55	$138.55	$138.60
Purchase #3	$102.70	10.331%	$113.3099	$113.31	$113.30	$113.30
Purchase #4	$91.83	3.152%	$94.7245	$94.72	$94.70	$94.70
Purchase #5	$150.37	6.341%	$159.905	$159.91	$159.90	$159.90
Purchase #6	$78.95	9.836%	$86.7155	$86.72	$86.70	$86.70
Purchase #7	$97.86	11.740%	$109.3488	$109.35	$109.35	$109.30
7 purchase totals =	$682.44		$743.3080	$743.31	$743.25	$743.20