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	$41.61	9.795%	$45.6857	$45.69	$45.70	$45.70
Purchase #2	$51.91	10.236%	$57.2235	$57.22	$57.20	$57.20
Purchase #3	$76.64	3.815%	$79.5638	$79.56	$79.55	$79.60
Purchase #4	$92.43	9.131%	$100.8698	$100.87	$100.85	$100.90
Purchase #5	$5.59	13.568%	$6.3485	$6.35	$6.35	$6.30
Purchase #6	$150.57	12.204%	$168.9456	$168.95	$168.95	$168.90
Purchase #7	$90.28	4.590%	$94.4239	$94.42	$94.40	$94.40
7 purchase totals =	$509.03		$553.0608	$553.06	$553.00	$553.00