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	$190.65	4.859%	$199.9137	$199.91	$199.90	$199.90
Purchase #2	$156.32	3.194%	$161.3129	$161.31	$161.30	$161.30
Purchase #3	$80.57	10.550%	$89.0701	$89.07	$89.05	$89.10
Purchase #4	$197.38	10.775%	$218.6477	$218.65	$218.65	$218.60
Purchase #5	$55.82	9.762%	$61.2691	$61.27	$61.25	$61.30
Purchase #6	$188.80	8.836%	$205.4824	$205.48	$205.50	$205.50
Purchase #7	$205.61	13.560%	$233.4907	$233.49	$233.50	$233.50
7 purchase totals =	$1,075.15		$1,169.1866	$1,169.18	$1,169.15	$1,169.20