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	$188.37	4.498%	$196.8429	$196.84	$196.85	$196.80
Purchase #2	$100.55	11.404%	$112.0167	$112.02	$112.00	$112.00
Purchase #3	$82.88	12.777%	$93.4696	$93.47	$93.45	$93.50
Purchase #4	$59.39	3.596%	$61.5257	$61.53	$61.55	$61.50
Purchase #5	$155.95	5.253%	$164.1421	$164.14	$164.15	$164.10
Purchase #6	$173.50	4.772%	$181.7794	$181.78	$181.80	$181.80
Purchase #7	$148.41	7.762%	$159.9296	$159.93	$159.95	$159.90
7 purchase totals =	$909.05		$969.7060	$969.71	$969.75	$969.60