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	$159.82	13.318%	$181.1048	$181.10	$181.10	$181.10
Purchase #2	$149.45	13.613%	$169.7946	$169.79	$169.80	$169.80
Purchase #3	$89.84	10.635%	$99.3945	$99.39	$99.40	$99.40
Purchase #4	$80.82	10.490%	$89.298	$89.30	$89.30	$89.30
Purchase #5	$163.97	6.776%	$175.0806	$175.08	$175.10	$175.10
Purchase #6	$73.55	3.824%	$76.3626	$76.36	$76.35	$76.40
Purchase #7	$250.46	5.421%	$264.0374	$264.04	$264.05	$264.00
7 purchase totals =	$967.91		$1,055.0725	$1,055.06	$1,055.10	$1,055.10