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	$167.34	12.224%	$187.7956	$187.80	$187.80	$187.80
Purchase #2	$38.49	13.603%	$43.7258	$43.73	$43.75	$43.70
Purchase #3	$48.57	12.785%	$54.7797	$54.78	$54.80	$54.80
Purchase #4	$48.33	13.648%	$54.9261	$54.93	$54.95	$54.90
Purchase #5	$83.52	13.650%	$94.9205	$94.92	$94.90	$94.90
Purchase #6	$119.75	7.246%	$128.4271	$128.43	$128.45	$128.40
Purchase #7	$199.78	6.283%	$212.3322	$212.33	$212.35	$212.30
7 purchase totals =	$705.78		$776.9070	$776.92	$777.00	$776.80