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	$85.33	8.741%	$92.7887	$92.79	$92.80	$92.80
Purchase #2	$82.72	8.615%	$89.8463	$89.85	$89.85	$89.80
Purchase #3	$51.87	10.839%	$57.4922	$57.49	$57.50	$57.50
Purchase #4	$181.87	4.623%	$190.2779	$190.28	$190.30	$190.30
Purchase #5	$102.40	11.411%	$114.0849	$114.08	$114.10	$114.10
Purchase #6	$100.71	3.219%	$103.9519	$103.95	$103.95	$104.00
Purchase #7	$49.41	10.676%	$54.685	$54.69	$54.70	$54.70
7 purchase totals =	$654.31		$703.1269	$703.13	$703.20	$703.20