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	$141.88	7.523%	$152.5536	$152.55	$152.55	$152.60
Purchase #2	$176.89	6.644%	$188.6426	$188.64	$188.65	$188.60
Purchase #3	$52.46	6.532%	$55.8867	$55.89	$55.90	$55.90
Purchase #4	$76.30	7.710%	$82.1827	$82.18	$82.20	$82.20
Purchase #5	$115.90	13.273%	$131.2834	$131.28	$131.30	$131.30
Purchase #6	$193.39	9.328%	$211.4294	$211.43	$211.45	$211.40
Purchase #7	$59.75	11.477%	$66.6075	$66.61	$66.60	$66.60
7 purchase totals =	$816.57		$888.5859	$888.58	$888.65	$888.60