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	$98.92	4.253%	$103.1271	$103.13	$103.15	$103.10
Purchase #2	$42.34	4.251%	$44.1399	$44.14	$44.15	$44.10
Purchase #3	$38.27	11.301%	$42.5949	$42.59	$42.60	$42.60
Purchase #4	$88.80	12.684%	$100.0634	$100.06	$100.05	$100.10
Purchase #5	$199.85	9.284%	$218.4041	$218.40	$218.40	$218.40
Purchase #6	$76.78	11.453%	$85.5736	$85.57	$85.55	$85.60
Purchase #7	$204.52	11.469%	$227.9764	$227.98	$228.00	$228.00
7 purchase totals =	$749.48		$821.8794	$821.87	$821.90	$821.90