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	$165.69	13.613%	$188.2454	$188.25	$188.25	$188.20
Purchase #2	$161.86	13.429%	$183.5962	$183.60	$183.60	$183.60
Purchase #3	$80.36	3.179%	$82.9146	$82.91	$82.90	$82.90
Purchase #4	$158.64	6.527%	$168.9944	$168.99	$169.00	$169.00
Purchase #5	$205.33	12.723%	$231.4541	$231.45	$231.45	$231.50
Purchase #6	$57.76	6.150%	$61.3122	$61.31	$61.30	$61.30
Purchase #7	$184.37	6.837%	$196.9754	$196.98	$197.00	$197.00
7 purchase totals =	$1,014.01		$1,113.4923	$1,113.49	$1,113.50	$1,113.50