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	$207.86	6.293%	$220.9406	$220.94	$220.95	$220.90
Purchase #2	$105.26	4.278%	$109.763	$109.76	$109.75	$109.80
Purchase #3	$63.85	11.401%	$71.1295	$71.13	$71.15	$71.10
Purchase #4	$191.56	10.728%	$212.1106	$212.11	$212.10	$212.10
Purchase #5	$100.61	6.444%	$107.0933	$107.09	$107.10	$107.10
Purchase #6	$98.95	10.685%	$109.5228	$109.52	$109.50	$109.50
Purchase #7	$150.55	10.348%	$166.1289	$166.13	$166.15	$166.10
7 purchase totals =	$918.64		$996.6887	$996.68	$996.70	$996.60