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	$164.61	7.869%	$177.5632	$177.56	$177.55	$177.60
Purchase #2	$239.77	4.599%	$250.797	$250.80	$250.80	$250.80
Purchase #3	$178.65	9.774%	$196.1113	$196.11	$196.10	$196.10
Purchase #4	$104.92	8.592%	$113.9347	$113.93	$113.95	$113.90
Purchase #5	$52.33	3.418%	$54.1186	$54.12	$54.10	$54.10
Purchase #6	$141.25	9.397%	$154.5233	$154.52	$154.50	$154.50
Purchase #7	$182.56	12.577%	$205.5206	$205.52	$205.50	$205.50
7 purchase totals =	$1,064.09		$1,152.5687	$1,152.56	$1,152.50	$1,152.50