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	$218.90	9.374%	$239.4197	$239.42	$239.40	$239.40
Purchase #2	$54.35	9.818%	$59.6861	$59.69	$59.70	$59.70
Purchase #3	$142.86	13.419%	$162.0304	$162.03	$162.05	$162.00
Purchase #4	$89.93	12.434%	$101.1119	$101.11	$101.10	$101.10
Purchase #5	$144.92	3.773%	$150.3878	$150.39	$150.40	$150.40
Purchase #6	$193.52	3.777%	$200.8293	$200.83	$200.85	$200.80
Purchase #7	$11.79	12.502%	$13.264	$13.26	$13.25	$13.30
7 purchase totals =	$856.27		$926.7292	$926.73	$926.75	$926.70