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	$51.66	3.845%	$53.6463	$53.65	$53.65	$53.60
Purchase #2	$115.96	13.756%	$131.9115	$131.91	$131.90	$131.90
Purchase #3	$179.85	6.488%	$191.5187	$191.52	$191.50	$191.50
Purchase #4	$65.73	6.739%	$70.1595	$70.16	$70.15	$70.20
Purchase #5	$81.62	5.346%	$85.9834	$85.98	$86.00	$86.00
Purchase #6	$181.85	5.757%	$192.3191	$192.32	$192.30	$192.30
Purchase #7	$231.29	12.766%	$260.8165	$260.82	$260.80	$260.80
7 purchase totals =	$907.96		$986.3550	$986.36	$986.30	$986.30