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	$208.30	12.469%	$234.2729	$234.27	$234.25	$234.30
Purchase #2	$124.89	9.392%	$136.6197	$136.62	$136.60	$136.60
Purchase #3	$154.75	7.366%	$166.1489	$166.15	$166.15	$166.10
Purchase #4	$142.67	3.585%	$147.7847	$147.78	$147.80	$147.80
Purchase #5	$223.69	7.126%	$239.6301	$239.63	$239.65	$239.60
Purchase #6	$55.71	10.577%	$61.6024	$61.60	$61.60	$61.60
Purchase #7	$62.76	7.158%	$67.2524	$67.25	$67.25	$67.30
7 purchase totals =	$972.77		$1,053.3111	$1,053.30	$1,053.30	$1,053.30