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	$80.56	6.657%	$85.9229	$85.92	$85.90	$85.90
Purchase #2	$62.65	11.858%	$70.079	$70.08	$70.10	$70.10
Purchase #3	$51.26	3.169%	$52.8844	$52.88	$52.90	$52.90
Purchase #4	$70.74	3.470%	$73.1947	$73.19	$73.20	$73.20
Purchase #5	$172.81	5.559%	$182.4165	$182.42	$182.40	$182.40
Purchase #6	$90.34	10.645%	$99.9567	$99.96	$99.95	$100.00
Purchase #7	$121.31	8.774%	$131.9537	$131.95	$131.95	$132.00
7 purchase totals =	$649.67		$696.4079	$696.40	$696.40	$696.50